This updated version isn't save game compatible since the  Kingdom Color Changer mod isn't updated to 1.6.0

Also, All credits goes to Nitrate55, the original mod author. I've just made some quick fix in the xml.
Check Original mod for more information. (like images. Sorry I've been a bit lazy to copy all of them :/)

I noticed that quite a few NPC clan banners were just generally messed up; i.e. sigils squished inside other sigils, asymmetrical sigil placement, and generally poorly designed banners as far as sigil placement goes. The only mod that fixes the various messed up banners is Unique Clan Banners and Modified Imperial Uniform Colours but I figured not everyone would want every clan to have unique colors as it makes it very difficult to tell where one faction begins and another ends since the clan banners are no longer uniformly colored for their faction. As such, this mod will serve as an alternative to that mod, though none of the redesigned banners in this mod are the same as the other mod. I redesigned the banners in this mod myself, before even knowing that other mod existed.

In addition, the redesigned banners here are as close to the original banners as I could keep them. The only exception to this is clan Banu Qild, who had the same banner as Banu Qaraz, for some reason. I created an entirely new banner for the Banu Qild in order to differentiate them on the map from the Banu Qaraz. Let me know what you think of it in the comments.

List of edited NPC Clan banners
Arkit
Avlonos
Banu Arbas
Banu Atij
Banu Habbab
Banu Qild
Banu Sarmal
Banu Sarran
Chonis
dey Arromanc
dey Cortain
dey Gunric
dey Molarn
dey Valant
fen Eingal
Harfit
Julios
Kuloving
Neretzes
Phalentes
Sorados
Vagiroving
Varros
Vizartos
Yanserit

Installation Instructions

Replace your existing \Documents\Mount and Blade II Bannerlord\Configs\KingdomColor.xml file with the one included in the mod folder.

Credits
This mod was created with the help of the banner editor site. I used the site to edit the banner codes I found in the spclans file. All I had to do was copy and paste the codes from that file into the banner editor site, edit as needed, then simply paste the new codes back into the file. This is a very easy process and you can do it as well if you want to change the NPC clan banners yourself.