ATTN: Byohazard.
From what i've looked through each Xeno has 3 different head customisations. the Warrior has three that look like dinosaur skulls, some of which look pretty sweet. The Spitter has 3 variations of the bulbous green sacs, with different patterns. ATM i can't remember all the Lurker one's, but the one that springs to mind was a really awesome looking one with no dome, a sort of spiked mohawk, and the original Alien face, so it looks kinda like a skull.