I found this nice little piece of software a while ago, right around the time I started my wallpaper collection from 4chan- obviously there was a connection.

Windows 7 (and I think Vista as well) has a built in background changer, which is nice, but this one has so many options you can change, then does all the work for you. I have a dual-screen setup, and because of how my desk is made, my monitors are arranged with the secondary to the left, which Windows doesn't seem to like very much. As a result, when I use a dual screen wallpaper with just the regular background selector, it reverses the picture.

With John's background Switcher, you just choose any pictures you want, then set up how often you want them to change, and how they should be sized to fit. In the case of multiple monitors, it can either display multiple pictures at once, or one very long picture, made to fit near-perfectly, even if you are running two different resolutions like me. You can even pull pictures off the web from various sites like flickr, or even I Can Haz Cheezburger to make a loltastic picture collage.

Even after I upgrade to Windows 7, I will probably still use this software. It takes up barely any processing power, and is very discreet but powerful. Click here to check it out, or just download the installer.