Arthur Gugick (torgugick) recently completed a printed tile mosaic of Einstein, using a new technique in which he overlapped the tiles, so that only a 1x1 square of each tile is visible. This allowed for greater resolution of the resulting mosaic, which he calls a "micro-mosaic".
The entire image is smaller than one 32x32 baseplate. Impressive.
In the future I would like to explore a bit of the history of the printed tile mosaic, and do a more thorough examination of Arthur's work, which is extensive. For now, here is a link to his mosaics set on flickr.