The parties/celebrations were a bit bare-bones or somewhat unfinished. Now there is more to them.

The same parties for 12 years... surely there´s time to read the mod page and/or browse the image section.
Approach
This mod expands what is already in the game scripts while using the same implementations done for each crowd involving event.
Simple applications fullfilling base potential and extras where needed to see it completed.

The info for each event described below are the changes made and do not demonstrate everything that is included.
Every detail in this mod is deliberate and for you to discover.

TL;DR - This mod adds to and fullfills underdeveloped quest events. It adds cut content as well not seen in any other mod. Basically, content that is already present in the game but not implemented and/or realized.
Take the bards festival, p.e., there are no theater seats for the npcs attending it, no guests, event stages are cut brief and ai behaviours are there also only as a base. Looking inside the scripts and quests the work is not finished/implemented, but the ideas are there. This event was meant to have different stages but only has one with barely a handful npcs standing static and out of place. You can see this in the image section with before/after comparisons. Its almost the same pattern for the other events.
Another example is the arch mage announcement, a new quest with a scene that was cut, underdeveloped and not implemented in the game. Now the title is acknowledged and celebrated by the mage peers at the end of the mages guild main quest.

This mod fleshes out the play, scenes, ai, guests, decor, dialogue, and for some new event stages, etc. As a result, the parties and crowd related events are more rewarding, more memorable and more meaningful.
I do hope it becomes more apparent why this mod would be of interest to you. Thank you.

    Party list 🥳🎉

    🎉 Thalmor party 
Added a few background guests to fill the place a bit. 4 nobles and a servant with their own behaviours playing with suggestion. No dancing, just lollygaggin.
Added 1 important guest from a dlc to suggest another weave of social-political power in this soiree.
The rest of the embassy building is left alone. What quests are completed affect what guests are present - this is unchanged. Scenes are unchanged.

     🎊 King Olaf´s Festival 
Added some decorative elements to the Bards College courtyard - lanterns, kegs, tables, chairs, minimal clutter and a Numinex reference - only active during the event.
Added 1 missing embers to the cooking spit. Added some idle variety in the courtyard. Weapons unequipped.
Changed Jorn and Ataf courtyard positions previously at a corner back against the wall. Now there is a chance to hear unique dialogue for the player and general conversations between npcs, which by default trigger with proximity. They start playing their instruments only after the event starts, same as in vanilla.
Previously only these 2 bards and the vendors were in the courtyard throwing words to the wind with nobody there to hear them. A player trap basically.
Added townsfolk attending this event. Some do not join the theater and are only there for foods and drinks, and possibly fun. Another example are the children that were present and now have their parents attending it as well. Among others.
In vanilla, npcs attend the event by being at the back against the wall and spread out in the theater. Changes were made to positions.
p.e. Priest Rorlund´s position between College members was changed. Now he´s beside Silana.
Added some of Skyrim´s bards. They now attend this event due to its relevance. Some bard npcs are excluded.
Lisette, a bard from next street now attends the event.
Giraud Gemane and Inge Six-fingers, the 2 other college teachers, now attend the event and take their place beside the other proeminent figures, Pantea and Aia.
Adonato Leotelli, from Windhelm, historian and known author of Olaf and the Dragon now attends the festival. Without going to details, this book relates to this event.
A representative from the court is also present now to oversee things on behalf of the Jarl.
The theater itself now functions as one. New npcs attending the event will take a seat there. Vanilla had 1 marker there for npcs to sit, that does not work or is used and thus was removed.  It will also look like the npcs are waiting for the player to arrive to light the fire.
New attendees number at 21.
The seats are present before, during and after the event. You can now go there anytime for group selfies. Take a seat during the event if you wish.
The crowd now has varying types of applause. You are to be commended. 👏 Congratulations ;)
The vanilla scene has been extended with a bigger round of applauses from a bigger crowd and a few bows in appreciation by the Bard´s College senior members.

On another note: typically when a quest ends the npcs involved scatter. This does not happen in this event - its vanilla - the npcs just stand there static because the npc packages were empty/unused. Also, leaving the city is the option to update the event to shutdown.
However. This left the suggestion that the party would go on through the night absent the player. Maybe, maybe not.
It has been done. Afterwards, the festival goes on to another phase after the ceremony as they move into the courtyard, where they eat, drink, sandbox, play music, dance and mingle. Rorlund, Inge, the children and their parents go home.
It then ends the same way it ended before, by leaving. It then takes 24hours to reset.

    ➕🍴 Namira´s feast
Added some elements to "flesh" out the room, if only to justify other elements already present.
p.e. There were trails and splatters of blood that lead nowhere and in impossible spots, either in the corridor that leads to the room, to the corners of the room, walls and high in the stone pillars. It seems the intention was to paint the town red and leave.
Changed the stray blood splatters to make a trail through the corridor into the room and towards the altar and on the ground. The splashes are more packed around the table as well and not dispersed and singled out across the room. None were removed or added.
Simple idle additions in case the player has follower company.
Added a bare minimum to the table and some cutlery instead of everything being bare-handed. Some civility is present, maybe just to pick the teeth.
What they are eating (already) does not come from someone´s freezer, so there´s that source represented as well.
Undressed the meatbag in the altar because the player does not eat clothing - only when on the altar; like in movies.

    ➕💀 Funeral attendance - Falkreath
More citizens of Falkreath attend the funeral. Previsously, 0 npcs were attending it. With this mod 7.
There is a spectator quest for this event but it is empty/unused by the game. Made use of this.
Npcs who attend are townsfolk who are outdoors, idle and non store owners. A court representative is there also. The town has fallen silent.

On another note, once the player arrives at Falkreath, the new attendances will fast walk to the graveyard. They won't be there at the ready. If you rush to the scene and they are still not there things will play out the same. Barelly requires waiting time. New players will likely follow them to see where they are going. This is preferable. Once the scene plays out they return to their routines. They leave after the mother leaves - same as in vanilla.

    🍹 Solitude Wedding
Before this wedding starts the temple´s courtyard has the 2 thrones and 4 noble chairs always present, rotting in the elements, awaiting the event. They were removed until needed. Alternatively, other decor was added to suggest another function for the courtyard, which in turn becomes disabled during the event.
A new common base guard npc was added to fullfill this.
Added some decorative elements for the event and some rearrangements for object positions, idles, planters, benchs and the white banners.
I would say only 6 npcs attendend the wedding ceremony. Kayd, the child, just stood in the back ready to point the finger with his field of view as a witness. Rorlund had his back turned all the time facing a wall, same as Jarl Elisif on the other side.
4 npcs took a seat. Nura and Vulwulf, Alexia Vici and Vivienne. Re-arranged all of the npcs positions without disturbing any scene. Except Nostrel - left untouched.
More seating places - previously 4 seats, now 12. Seatings are a luxury in a royal wedding. The Jarl takes a sit in the front. 
Thane Bryling and Erikur are present in the script, but unfulfilled. They now attend the ceremony.
Erikur´s sister, Gisli, persuaded her brother for a seat. Imperial friendly Whiterun´s Battleborns will attend.
Some important figures that like parties attend the event, suggesting a weave of social and political power.
New guests/witnesses around the area - Kayd´s parents are now present (Bits and Pieces store will be closed), and other townsfolk. 
Depending if some npcs survive some quests there are  24 new guests at this wedding.
After, in vanilla, what is added to the event remains after the event, that is decor remains like food and all the other stuff. Now its all back to the way it was, to the new default.
One of the gate entrances will be open again as well.
If the player went the statue route, the statue debris is still there after the event. However the enable toggle option is also there without functioning. Decided for a clean execution - to remove the toggle prompt from the statue, and at the same time removing the debris, thus restauring the statue afterwards.
One of Gabriella´s elven arrow was not assigned correctly and was present all the time.
Gabriella´s bow on the platform - unchanged from vanilla - will now disappear from the game if the player does not claim it at the time of the event.
The Penitus Oculatus agent was another example that remains in the spot afterwards. Now, when the quest advances he´s not there anymore, idling forever where was last seen. Vittoria Vici´s body lingering was also another thing despite having/not having a cleanup script.

On another note, attend to the courtyard, hear what the npcs have to say, sit down, relax. The speech and the sitting on the throne are a back and forth loop. The speeches are varied. Ample (infinte) time for business - same as vanilla.

    🍸🥳 Player Wedding
Full house now, vanilla style!
In vanilla there are 3 witnesses for the player and 3 for the love interest, with a total of 8 guest seats, with 2 child markers.
In this mod the number of player witnesses and guest seats are expanded.
Inside the temple, switched the type of benches during the event (quest only). Before each bench had 2 seats, now each has 3. Now boasting 8 benches instead of 4. 
All eyes are on the player, allies, confidants and friends, from all sides, to leave the Dragonborn red-faced.
Full, fun and random, everytime. The less you complete the game at the time of this quest, the emptier it will be. Or the more interesting combinations you get.
Adjusted a priest chair clipping animation in vanilla during the ceremony and a couple of misaligned rugs.
Love interest now with weapons and shields unequipped.

Vanilla Scene edits:
Before, the priest started the ceremony dialogue before the player could reach its designated position at the altar. Added a delay to put the timming right.
Headtrack change while answering the question.
At the end of the ceremony npcs will give you and your love interest an applause. You are to be commended. 👏 Congratulations ;)
Extras
In vanilla, there is a post wedding scene with the purpose to forcegreet the player to make a house decision with the spouse. This was taken further.
Added some decorative elements at the Temple´s courtyard that appear only during the quest, progressively, before and after the ceremony.
The quest now has a reception at the courtyard before the ceremony and later a party in the courtyard, where your random guests mingle - what they are assigned to do there is also random.
This is the only event where it would justify a get together of various distant npcs, having them interact in the same space and to justify bringing some sort of closure to the players journey. This was another step to make this event much more eventfull and satisfying while providing some measure of roleplay.
Dialogue was included to provide consistency throughtout all the stages. Also all outdoor npcs inside Riften now acknowledge the wedding and congratulate the player during the event.
It then ends after 9hours pass.

On another note, In the images many of the npcs are Stormcloaks because that is the campaign I had. You can get dlc npcs too.

    ➕👥 (extra) Solitude´s execution 
More npcs attend Solitude´s opening scene, some that you don´t see normally or at all and yet reside in the city.
A court representative, townsfolk and workers. Silana, included as a quest alias was not present. Now she attends the event.
Previously, 10 npcs. With mod, 22.
Small extras for you to notice to give it a bit of drama and life (varying npc behaviour while watching the event).
Some of the npc packages have been changed a bit to ensure the timing of arrival an exit from this scene is right.
p.e. Beirand who was almost always late now fast walks to the event, among others who that can happen. p.e. Taarie and Noster lingered too much afterwards.

    ⚔👥(extra) Better Morthal Opening
A bigger crowd at Morthal´s opening scene. Pitchforks are out and citizens are checking out what the fuss is about. Maybe its dangerous living among wizards after all. Now the guard stationed there has a reason to watch over the unrest.
Previously, 4 npcs, now 13.

    👥👏🧙‍♂️ (extra) Better Arch Mage Announcement
You are named Arch-Mage. Here´s the new clothes and the new key to the new quarters. That was it.
There is an unused scene with 10 npcs with small dialogue cheering the player´s newest achievement. In it, Tolfdir announces and presents the player as the new Arch Mage to the other College members. While it plays, Faralda and Tolfdir give a very brief applause.
This scene has been worked on, expanded and more, and implemented into the game. It is a short scene.
After completing the Eye of Magnus, a new quest will appear to Visit the Arch-Mage quarters, which is the logical follow-up after Tolfdir delivers your new ownership dialogue.
Now, instead of a dump finish there is a sequence and a scene to end on a high. You are to be commended. 👏 Congratulations ;) 

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That´s all the game events I wanted to change.
No intention of adding celebrations here or there that are not part of the base game already in some way.
Mod added npcs could be integrated in this.

Events left out with crowds
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This mod edits the following quest scripts
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Compatible mods ✅  a list of mods that are compatible by default
Ussep - this mod uses some of its scripts as a base - recommended but not obligatory. It fixes so so many bugs, get it. 1.97 USSEP pre-AE download link 
on another note,  you might want the patch on the author patches page for it. 
King Olaf's Fire Festival Not Ending Fix - recommended alternative (also in USMP). Better Skyrim Parties already includes shutdown ending scripts from Ussep to address the same issue. Overwrite what you want, if you want. edit: because I have an esp mine will prevail always, I think.
Better Effigy of King Olaf - recommended
Namira shut down quest - recommended (also in USMP) - not included here.
Npc AI Process Position Fix - NG - recommended for the player wedding - it will improve transitions for npc positioning from the temple into the courtyard.
Namira for good guys
New Namira statues
Brotherhood for Good guys - don´t know
Immersive Citizens
Holidays
Cutting Room Floor
Immersive world encounters
Buvarp´s
Compatible with all College of Winterhold mods
Open cities - needs a patch
Sepolcri
COTN Falkreath
The Great City of Falkreath
Colovian Falkreath
The Great City of Solitude
Redbag Solitude
Spaghetti´s Cities
Script mods
ELFX and ELFX Shadows
Lux - Load Lux below/after
Distinct interiors
3dnpcs - don´t know if it benefits some integration
Recommended use of diverse sitting animations and standing idles to spring some life into the new crowds, and possibly some dancing.
Any mesh and retexture
Marry me Serana mod compatible

⛔ Not compatible with Marriage mod - to have and to hold ; probably other marriage mods that edit the same thing. Simply do not select in the individual files the better player wedding.
Destinations weddings - not compatible
Better Wedding Guests - not compatible - this mod has a different approach.
Animated Wedding Scene SSE - if the mod includes the ussep fixes then just let it overwrite Better Player Wedding, if not, it needs integration and recompiling in a patch.
Multiple marriages - do not know, flagged as incompatible.
Wintersun - Better Funneral Atendance, AIO - source scripts are not available so I won´t be able to make a patch for it. Incompatible, or just overwrite.
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💠 Some patches already available 💠
Better Skyrim Parties - Author Patches  
Ussep
JK Skyrim AIO  - Solitude
Dawn of Skyrim  - Solitude and Player wedding
Enhanced Solitude
Redbag Falkreath
JK´s Temple of Mara - Player wedding - if the priest is out of place in the ceremony try fiddling with the load ordrr.
Ai Overhaul - Better Solitude Opening, aio
Buvarp SE RE - Chronicles of the College
Tales of Skyrim - Berserkyr
Npc replacer patches  - some patches provided for Better Solitude Opening and Better Skyrim Parties AIO ; not needed for the others.
Vittorias Alternate Wedding 
Dark brotherhood Reformation
About Roggvir
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All files are espfe´d. esp-esl.
This mod has no requirements.
Performance measure: If you can be in any city you can run this.
Works mid-game I guess; not the recommendation.
Not good installing this while running the same quest/quest stages, it will cause issues.
Same thing turning this on after said quests.
Also not good to change from an individual file to the main aio file.
Uninstalling and continuing the same save is the worst you can do.
New save game is the way to go.
New dialogue files are reused voice files from Pantea in Solitude's wedding. A simple swap renaming them will do for another language.
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troubleshoots and questions I think may be asked

You do not need to read below