AndreaMosaic is a free portable tool which makes it easy to create photo mosaics, images which are themselves made up of other images. (Not sure what we mean? Check the Samples page.)
The program has only three core steps. Choose the source image; point it at the images you'll use to make up the mosaic; then click the Create button, and wait as AndreaMosaic selects and arranges your images to produce the best result.
If you don't like the default settings, though, there are plenty of tweaks available. You're able to choose the mosaic size and resolution; the number of tiles, and their arrangement; how often tiles may be repeated; how much you'll allow AndreaMosaic to change the tile colours, and more.
There are surprising extras, too, including the ability to create your mosaic using frames from a video. Just point AndreaMosaic at your source video and leave it to work.
The program's interface isn't always straightforward. It doesn't make it immediately clear what you need to do, for instance, and the process of selecting your mosaic images is flexible, but over-complicated. You will have figured out everything you need to know in less than five minutes, though, and on balance it's an excellent mosaic creator.