http://lifehacker.com/featured-desktop/ - on the sidebar here I found most of these wallpapers.
Avengers, Super Mario Brothers, Firefly, Coke, Battlestar Galactica, Star Trek, Muppets, Alice in Wonderland, Lord of the Rings, Star Trek, Fringe.
Super Mario Bros.
Coke (This is how it looks in Tomorrowland at Disneyland)
Star Trek Original Series (Life Science, Instructor, Engineering, Command)
Also found a really cool screen saver over at http://www.mewho.com/system47/. It basically looks like a computer screen from Star Trek and if you have the sound on it sounds like the computers on ST too!
Alice in Wonderland
Lord of the Rings
Star Wars (Rebel Alliance and Empire)