This is a test of a pixel art build from this webpage
(with permission from the creator). I thought I'd give it a try, since making 2D pixel images is a common Minecraft pasttime. I made this one 3 mm thick, making it noticeably more expensive, though I'm sure you could make it 2 mm thick.
One cool pixel-art trick (that I don't use here) is to make the model twice (or more) as thick by adding more blocks. Colored sandstone material models have to be 2 mm thick or Shapeways won't print them. This model here, is printed at 1 mm per block, and the creator just doubled up the blocks to get to 2 mm. On the backside he made the panda's eyes a different color.