The answer lies in the way appearance.2da affects your uh, appearance.
What KSE does is to change the appearance.2da lookup record for you or your party NPCs. The numerous columns in that .2da file define what textures are used for the different robes, armor, etc. You can use KotOR Tool to make any necessary modifications you like. Uthar, for example, has the same textures defined across each of the columns.
This appearance.2da walkthrough provides a lot more detail.