Thing 6 Flickr Mash-ups

The whole concept of mash-ups is new to me. Several looked fun to me, but I particularly liked Montagr. My son used to have a Star Wars poster of little mosaics that put together formed Yoda that was like this. I've been looking for a site that takes one photo and divides it into tiles to make a wall-sized poster. I saw this on an HGTV show. If anybody knows where I can find this, let me know!