Thank you very much for the kind words! I actually planned it using a 130px x 130px file in Photoshop and just drew it that way. After it was done, I counted each pixel and found the best possible colors/sizes/prices for pieces on either BrickLink or Pick-A-Brick. All of the pieces are either 2x2 or 1x2, except for the base plates and the 4x4 and 4x8 plates that are underneath the elevated characters and the frame. When it came time to build it, I just built each 32x32 plate on its own (cropped in Photoshop so I didn't get confused) and put them together like a puzzle at the end. I used two different kinds of 3M sticky things to mount it. One was just this standard double-sided 3M foam tape that comes on a roll - that was used to get each plate to stick to a 40"x40" foam core board. Then, to hang the board on the wall, I used the large 3M "picture hanging" adhesives, which worked surprisingly well. They say they can hold up to 15 pounds or so, and the portrait was fairly light since I used the foam core backing (I'd guess around 7-8 pounds total). The only difficult part was lifting it above my head by myself - while holding it perfectly level - on Christmas morning to stick it onto the wall. But it worked!
Here's the link to the original 8-bit portrait I based it off of: http://drbl.in/CpE