Using stickers (or even laser engraving) to customize your MacBook is nothing new, but what I think sets MacSlaps apart from some of the others I have seen is the designs are simple and creative. In addition to the Lego design pictured here, their site showcases a few other interesting designs, such as Mario, PacMacMan, and my favorite, Tic-Mac-Toe.
The stickers come on a square sheet of vinyl, ranging from about 4 to 8 inches, so most of them will even fit on the 13-inch MacBook. I know they say these are custom made for MacBooks, but I'm tempted to order one and try it on the back of my 24-inch aluminum iMac, since I'm guessing the effect would be about the same. They also offer custom designs, so if you've got a crazy idea in mind, they can probably help you get it onto your Mac.
Although the selection is pretty sparse, their designs are original and interesting. Plus, it looks like they've just recently started up, as their Etsy store opened in October, and some of their designs haven't shown up on the store yet, so I hope this means we will be seeing more from them in the near future.
All in all, these stickers would make a great stocking stuffer for your favorite Mac geek. Not to mention, if you're picking up a new MacBook for the Holidays, they are a great way to add a personal touch, especially with the custom design offer.