Halo Combat Evolved
Halo 3 wallpaper Made by Woolybear - Woolybear@censattwb.com
Spade6179 has given us a background pack. It contains pretty pictures of CE maps that you can use as your backgrounds.
25 wallpapers in 1280x1024 and 1024x768 from CMT's single player mod captured by Agammenon.
A Halo wallpaper made using Unreal Tournament 2004 and some Skin Packs.