I have the same thing - any custom race I make doesn't pick up on the mouth textures in the BSA. Dunno why, used to be fine before I installed TKs Eyelashes, but even though I've since re-installed the entire game, I still get this. I fixed it by extracting the relevant files from the BSA (I extracted everything in textures/characters/mouth, into the same folder structure), and directing the GECK at the extracted files instead. Works fine for me, though is a little annoying. Wish I knew why it doesn't pick them up itself! Hope that helps!