MultiWall offers thousands of wallpaper downloads and lets you do more with them. You can rotate, cycle, and even switch them on a set schedule. The best part is that it supports multiple monitors, which many programs can't promise.
With MultiWall, you get dozens upon dozens of wallpaper downloads that you can put into a rotating list. You can change them and cycle them as often as once every minute to once a week. All of the wallpapers are in a very high resolution, but they can be cropped to fit your monitor, automatically. The program is a bit of a RAM hog. When running, it took up as much memory as a browser or other power-packed download. That's a little extreme if you're auto-rotating, because the program has to run around the clock. If you use multiple monitors, MultiWall has several options specifically for you. It lets you display the same wallpaper on each or change them to two completely different streams. You can even import wallpapers from a few places on the Web. There's no built-in support for Flickr and other sites, but you can yank pictures from those if you know the URL.
MultiWall offers more options and features than many other wallpaper-changing downloads. It's really nifty that the program supports multiple monitors without much setup. If you use two, three, or more monitors in your office, this is a neat way to decorate them.