Awesome

photomosaic

Assemble thumbnail-sized images from a large collection into a mosaic which, viewed at a distance, gives the impression of one large photo.

Documentation: http://danielballan.github.io/photomosaic/docs/

Related Work

John Louis Del Rosario also has a photomosaic project in Python. I studied his code while I began writing version 0.1.0 of this project in 2012, and there were similarities. Version 0.2.0 (2016) is a complete rewrite that takes a fundamentally different approach.