Jake of the Web

Although you have undoubtedly seen a photomosaic before, you may not know what one is. A photomosaic is a picture made up of many smaller images. One of the movie posters for The Truman Show is a prime example of this:



There is software out there that enables you to create your own Photomosaic:

Photomosaic maker – Perhaps the easiest to use by virtue of gathering other people's images for you, 'Photomosaic Maker' collects pictures from Flickr.com and forms them into a mosaic of any image you upload.
Photomosaic Maker

A more intense (but therefore with more customizable results) is the downloadable photomosaic maker 'Andreamosaic'. Andreamosaic allows you to use your own pictures (select a folder or folders on your hard drive) to create the tiles of the mosaic.
Andreamosaic allows a lot more customization of the end result (number of tiles, what pictures to use, how often a picture can be reused, etc) but is relatively processor-intensive and can take some time.
Andrea Mosaic