I was trying to clean out my bookmarks in firefox (another long topic entirely) and I stumbled onto this site. The download is windows only (so sadly I haven't had the chance to test it out). But what the app supposedly does is takes multiple photos and it takes all those photos and makes a mosaic of a bigger photo. Kind of like the feature in one of the main mac os x screensavers where it takes photos from iphoto and makes a mosaic of a larger picture.
Unlike that screensaver you can actually save the image and again it's windows only. The app is free (which was partially why posted this). If you try this app feel free to leave a comment! When I have time perhaps I'll try it out too.
It works in windows xp, vista, and 7.