grab a trio of new wallpapers for Wrath of the Lich King, including this handsome shot of the lichy monarch himself (although every time I see this armor, I can't help but think of Private Ownsusohard's "im the lich king lol" silliness back at BlizzCon).
There's also a shot of Arthas rocking Frostmourne, and a screenshot of that big furnace inside Utgarde Keep (which has been around for a while, but still looks cool. If you're looking to adorn your desktop with some cold and snowy images while the weather heats up outside, there you go.
In fact, almost any of these Wrath images might work for you. The sizes aren't actually wallpaper, but with a little tweaking, you could pretend you were in Northrend already.