etherdoodle
Etherdoodle is a collaborative canvas where users participate in the creation and transformation of images by purchasing pixels on the Ethereum blockchain. The etherdoodle canvas has dimensions of 1000 x 1000 pixels, for a total of 1 million pixels, each corresponding to a unique digital token. Pixels can be purchased by users at any time, in which case the original owner will automatically be re-paid their principal payment, plus a built-in cost increase that rises each time the pixel is exchanged.
The contracts folder contains the solidity code for the token and a deployed version of the contract can be foudn at https://etherscan.io/address/0x7f53080daefbf41e727fdaff1538ef6052ddb994.