I just began a new page of cool Sci-Fi texture images. Give it a look:
I'll be adding many more images, including skins for creatures, aliens, etc.
Btw, I've also had folks ask about how to credit me for my images. Please simply list me and my website under "Textures" in your credits section...there's no need to identify which images are mine...unless you really want to. :-)
Anyhow, I think this is going to evolve into a really cool page. Hope it's helpful!