Tyler Clites (Legohaulic) recently posted this little mosaic that he built ten years ago when he was 14. It is the LEGO logo done in graffiti style. When I first saw it, I expected it to be much larger than it actually is.
I found some other mosaics in his photostream too. The first one shows lettering on a Bible. I was particularly impressed with the gold he used, since that color is available in many fewer parts, which are generally much harder to work with.
I also notice that his buddy icon is a mosaic incorporating the L and the H from his user name.