update 18Th Oct 2008 : the below wallpapers which used to exist on the old GW site do not exist on the new one. I will populate this post when (or if) the new site is updated with wallpapers.
There are a mixture of desktop wallpapers, some photos of minis, some army book artwork and some other pictures I haven't seen before - some of which are awe-inspiring. The hardest decision is which one you'll put on your desktop !
Downloadable and Free Desktop Wallpapers
Beasts of ChaosBretonnia
Empire
High Elves
Hordes of Chaos
Lizardmen
Skaven
Tomb Kings
no desktop wallpaper found at GW UK but here's some artwork instead:-
Dark Elves
Dwarfs
Ogre Kingdoms
Orcs and Goblins
Vampire Counts
Wood Elves