One of the most trivial (yet my most beloved) features of Windows 7 is the built-in ability to slide-show (shuffle) wallpapers.
The wallpaper chooser in Windows 7 looks much like the one in Windows Vista, except that when you hover your mouse over a wallpaper thumbnail in Windows 7, a checkbox appears on the image. You can therefore choose one (or more) wallpapers, then choose how often to change them, and whether you want them to be displayed in the order chosen, or shuffled. It’s a tiny little feature, but one that was long overdue in Windows.
What’s even cooler is that you don’t even have to use the Wallpaper applet to get the party started: you can also simply highlight a bunch of pictures in any Windows Explorer window, then right-click and choose “Set as Desktop Background”:
It’s really a nice little touch!