What The Mod Does
When fallout 4 is launched, the F4SE code takes in 25 jpg/png/dds images from a folder specified by the user. If there is more than 25 images in the folder the code will randomly pick 25. Then using Microsoft's DirectXTex library the jpg/png/dds images are converted to dds, resized to a 1:1 aspect ratio and placed into the fallout 4 textures folder. Next the game loads in the images and assigns them to a loadscreen. Each time a load screen appears there will be a different custom background!

For the most part this mod is complete, I will update for bugs and maybe a few smaller features.

To re-enable loading screen overlay text, delete Interface/LoadingMenu.swf or use options from No Text in Loading Screens

News
I recently created a mod using the same underlying idea to randomly shuffle music from multiple music mods without the need for an esp patch, give it a try!
Automated Sound Track Replacer (ASTR)

PERFORMANCE NOTES
Note: When referring to performance with this mod, it is initial load time with the game launches, this mod has little to no impact to in game performance.

Search for HighFPSPhysicsFix setting in the F4SE/Plugins/ALR.ini is enabled by default and will only be disabled by the user, if HighFPSPhysicsFix applied:1 and you have no plans to reinstall HighFPSPhysicsFix then it can be safely disable to reduce some runtime overhead, but it's likely minimal.

Currently the mod will... 

• Resize images which do not match the aspect ratio (high performance cost)
• Upscale/downscale images when appropriate (high performance cost)
• Decompress compressed images (mostly applies to DDS)
  

With a high performance NVMe SSD it takes around 15 seconds to load the game when decompressing and resizing all images to 4K resolutionsBecause of this it is highly recommended to use decompressed images that match your aspect ratio and resolution to your monitor's resolution and aspect ratio

Resolution Support
This mod now supports more than 16:9 :) here are the monitor aspect ratios supported and what res resulting image will be loaded in game:

1:1 AR 2048 2048 2k Res, 4096 4096 4k Res 
16:9 AR 1920 1080 2k Res, 3840 2160 4k Res 
16:10 AR 1920 1200 2k Res, 3840 2400 4k Res, Apparently 4K 16:10 monitors don't exist, probably will never be used

~21:9 AR
21:9 AR 1260 540 2k Res, 2520 1080 4k Res, Not really a resolution used, Standard is 64:27 :/
64:27 AR 1280 540 2k Res, 2560 1080 4k Res 
43:18 AR 1720 2048 2k Res, 3440 1440 4k Res 
12:5 AR 1920 800 2k Res, 3840 1600 4k Res 

Completed, in 1.1 patch

• Fixed issues with background image replacement not properly scaling the image
• Added option to disable background image replacement, disabled by default since it adds more conflicts with mods that change loadscreens
  

Completed, in 1.0 patch

• No DLC Version
• All input image resolutions are supported
• Support for non 16:9 monitors
• Support for 4K outputs, only when input image is 4k and monitor resolution is 4k
• Compressed and DDS input images support
• Image color quality is better retained
• Loadscreens sounds will no longer be player, and images cannot be moved
•  High FPS Physics Fix compatibility patch
• Removed loadscreen overlay
  

Completed/Will not be implemented
• Fix for virtual folder based mod loaders (MO2) Not Possible
  

• The folder which the dds files are stored cannot be deleted Support Added
• The LUT overlay on the background image causes the color of the image to change slightly, I can improve this but I'm not sure if I can fix it Fixed
• Converted files will not be deleted from the textures folder when the game is closed Support Added
• Since 25 images is a little limited I will probably make it 50 at some point, it just takes a lot of time Redundant, Will not be implemented
• Reduce runtime through multithreading Not Possible
• Rebuild deleted file paths (ex. ALR_Backgrounds) Support Added
• Create default image directory Support Added
• Option to disable image reloading Support Added
• DLL checks to ensure mod was correctly installed
• My code is messy and likely contains methods that are considered "bad practice" and could be improved to be more efficient, I will release the code on github once it is in a state I am happy with Link Below
  

Compatibility
This mod is incompatible with any mod which adds/removes 3D objects, so remove the modifications through F4Edit (I detail how to do this in a pinned post of my No 3D Objects Mod)

Install Process

• Install F4SE
• Install this mod
• Set a path in ALR.ini, install a premade image pack (links below), or  add photos to (Data/F4SE/Plugins/ALR_Backgrounds)
• Launch The Game!
  

Source Code Link Here!

Premade Image Packs
Intro and Endings in Color for Automated Loadscreen Replacer - kinesthesia07
random concept art loading screen - dmc99
FROST - Screenshot Contest 2022 - Loading Screens - LukeCastellan
New Vegas Load Screen Replacer (v.2.0)  - MaddieMac04
TOVOT simple screens - 7OVO7
 Ultrawide ALR Loading Screens (3440x1440) 21x9 - js303
Pinup Girl Loading Screens for ALR (16x9 and 21x9)- js303
Loadscreens Of Decay - AltHenryy
The Outer World's inspired Loading Screen's - Scrim3s
Upload a pack of images to Nexus, and I will link it here!


Mod suggested by MisterOldVegas