Mouths of Lexx : Xev 1 Close up of the Clay Xev-1's mouth and a picture of Xenia Seeberg, the actress who played Xev in the LEXX series.
Kai, Stan, Xev, Prince
Don't be afraid to sculpt real people. In some ways it's easier because there's a focus to the practice.
Always practice on people you love to look at a lot, for there's a lot of practice that's needed to capture a likeness.