Simple question. In the vanilla ESMs there are several falling rock activators (TrapFallingRocksSm01, TrapFallingRocksSm01_CaveGBoulder, etc) that all point at the same NIF (trapfallingrocksm01.nif). When previewing in the CK and loading them in-game, they each have a different texture applied. When I extract and examine the NIF, though... there's only one texture mentioned.

I now have a mesh I want to apply 13 different textures to. How can I replicate this trick to allow me to include 13 objects all pointing at the same nif, but with different textures applied? Right now it seems like I have to make 13 different NIFs with 13 different BSShaderTextureSet properties.