Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
Photo mosaics are recreations of one large image composed of tiny tiles of other smaller images. They can be a fun project and make good use of the hundreds of less-than-extraordinary photos on your hard drive. We compared three easy-to-use Linux-based utilities for generating photo mosaics -- Pixelize, Metapixel, and Imosaic -- on speed, quality, and other factors.
Pixelize is the oldest of the three apps; it uses GTK1 for its interface, which may make it stand out from your other desktop applications. You won't be able to use your favorite file selection widget, either, which can be frustrating -- the GTK1 file selector does not remember the last directory you visited, and it does not provide thumbnail previews of image files.
Metapixel is a command-line-only tool, but it offers more flexibility in mosaic creation than does Pixelize. The latest release is version 1.0.2, which you can download from the project's site. Source code as well as Fedora RPMs are available. But as with Pixelize, many modern Linux distros ship Metapixel, so see if you can use an official package if you are not interested in compiling your own binary. Metapixel requires Perl for its image preparation step.