For one of my zones I worked out that the way we would theme the various boss fight areas was by using different statuary. But since they were going to be big full characters anyways, why don't I just make them as normal NPC's and then we could also use modified versions of them as the actual bosses you fight; like statues come to life. So in this particular case - since I knew that they'd be around a lot - I made a base body and put that on one set of textures and then took all the various parts of their unique armor and put them on another set. This way I could mix and match the statues together with fewer render calls and at the most it was only two shaders per NPC anyways. Overall I was pretty happy with the way they turned out.