The Kompetenzzentrum Mensch-Maschine-Kommunikation has an interesting freeware for Microsoft Windows called:

ImageSorter

Don't let the relatively mundane name put you off. Head over to their website linked above and take a look at some of the sample image sortings presented. They describe this way: The current version of ImageSorter sorts images by the similarity of their color layouts. Future versions of the program will support additional ordering criteria.