How to Make Your AI Unique
From The DarkMod Wiki
written by Springheel
Running into clones of the same AI over and over again can damage a player's suspension of disbelief. Beyond that, it's just plain boring. Luckily, there are some fairly easy ways to make your AI look a little different from each other.
Skins
An easy--and quite effective--way to make your AI quite different from each other is to use an alternate skin. A skin is basically a different texture from the default. It could be as simple as changing the colour of an AI's tunic from blue to green, or a totally new texture that changes the clothing entirely (though obviously the basic shape of the model remains the same).