What race are you changing into draenei then? I have done troll male -> draenei female and it worked 100%. One thing I noticed was that model viewer didn't display some textures correctly (one certain hairstyle had armor textures instead of hair textures) but they were perfectly okay in game. And yes I did add all those empty Scalp blps. Trolls also had "FacialUpperHair##_##.blp" and "FacialLowerHair##_##.blp", which I also replaced with blank ones. You might want to try looking if there are similiar textures on your race. I am assuming here that the extra hair textures you are seeing are from the original race, not from draenei - that shouldn't happen

Oh, I might also add that it's very easy to check what textures it's loading, and then check them. You see, model viewer writes them to its log. Clear the log, run model viewer, select your original race and see what textures it loads. I hope this helps.