Custom appearance on many NPCs

I need a lot of low poly character on screen at once, maybe up to 100, will there be complications if these all have some difference in appearance? They need difference clothes ("brands" and color variations) and also different facial features ("pasted on" eyes, mouths etc).

Think the Xbox avatars but even more low poly. Will the difference in textures make it too many draw calls? Or what is a good solution to add different set of eyes for example, for many of the characters? I would like eyes, mouth and so on to be animated textures only and not changes in the head mesh.

So it would basically be a couple of base meshes for the bodies and heads. Then a set of textures for eyes, mouths, scars and so on to put together to give the NPC custom appearance.

Hopefully someone could point me in the right direction.

 

You might want to look into composited textures.

Which is unwrapping the characters to one UV sheet, keeping the islands for each part in the correct place, then you create the texture for them by having a base texture (just skin) and blending on top parts from other textures. This all composited to one run-time generated texture per character.

Brink uses a system like this - worth doing some Googling on their character variation presentation.