The 'Shop Contest we run on weekends is for bragging rights only. deviantART don't fuck around, however. It's offering a $10,000 cash prize to whomever sends in the best wallpaper in a promotional Gears of War 3 contest offering a lot of other loot to the runners-up, too.
For the first time, deviantART is permitting collaborative entries, too, so if you and a buddy can activate Wonder Twin powers, you'll divide a prize package including $10,000 cash money, a Gears of War 3 limited edition console bundle not unlike the one recently unboxed by Ice-T, a one-year premium membership to deviantART and other fun stuff. Or go stag and claim it all for yourself.
Second and third place will get $1,000 and $750 respectively, the game, a 4GB Xbox 360, and various other swag. deviantART says there will be 100 cash money winners in all.
See the link for the official details, rules, requirements, and the asset pack that'll help you build the wall, which may be used by Microsoft down the line for promotional purposes; i.e. it becomes property of The Man, but for $10,000 and a bitchin' console that's a pretty good commission, I'd say.
Gears of War 3/Artists United Contest [deviantART]