Twenty pixels square isn't a lot of space in which to be drawing your masterpiece. Do your best anyway. Add a link to your image in the comments section.
Ketchupart.com, without a lot explanation, features a bunch of pictures of plates decorated with intricate (and not so intricate) drawings done with... ketchup, natch.
Please think twice before buying from Todd Goldman's David and Goliath t-shirt company. While some of these allegations of stolen designs are questionable, other are pretty blatant and, therefore, shine a harsh light on the questionable examples.
5. Ping Pong Pixel
Computer aided, automatic, over-sized photo replication in multi-colored ping pong balls.