Matt De Lanoy (Pepa Quin) recently completed an amazing series of mosaics based off of characters from the comic The Order of the Stick.
The mosaics are highly complex, as you can tell by this shot of the back:
Matt has an explanation of the process he used to make these mosaics if you click through on the above photo. You can also find individual photos of each of the characters in his photostream.
Matt has an amazing body of prior work that I've been meaning to highlight. In the meantime, be sure to look through his photostream to see some fantastic LEGO creations. Also, thanks to Bruce for the tip.