Excellent skull assortment. Reminds me too of the Predator movies. Some people are freaked out by this stuff, but I think it is fascinating.
You might already know this, but it's worth mentioning in case you are curious. A friend of mine has been collecting skulls since we were boys. He has any animal you can think of, including elephant skulls. When he gets a new head, he uses his special colony of Dermestid beetles to clean them. Sometimes he doesn't have to do anything to it, except drop it in the beetle enclosure, and two weeks later it comes out bleach clean. You can actually buy these beetle kits online now, but I have no experience doing it.
My favorite skull is the wolverine. It is like a miniature bear skull. We have spent hours studying the skulls, him much more than me, since he has the collection in his house. Haven't seen him in a while since he lives in Alaska now.