ThetaWall is a freeware program which turns your boring old Windows wallpaper desktop into a groovy slideshow using your photos. Just point the prog towards a sub-directory of images and it will update the desktop image every 5 minutes (or on demand with a double click).
It likes memory (runs in 20MB of RAM, plus whatever it needs for the images) so watch out if you’ve got large images to display. On the plus side it’ll cope with multiple monitors and also features a screensaver option, which is cool.
ThetaWall changes desktop wallpapers periodically using the image files it finds in subdirectories. Perfect for your single-monitor, dual-monitor, triple-monitor, and multi-screen computers, ThetaWall knows how to span images across displays, make collages of many photos, or simply put one image on each monitor. It includes options to enlarge and reduce images to fit, and can even act as a screen saver. No installation is required if you already have the .NET Framework.