Facecoin Cash is a new higher-resolution, lower pixel bit-depth advancement on the original Facecoin.
Facecoin is one of my most popular projects. It's a good introduction to some of the technical and ideological ideas behind Bitcoin and other cryptocurrencies.
This new and improved version produces larger, more defined images with clearer "face" identification. It has the same block size though.
See it in action here:
Part of the Coins project.
Cryptocurrencies such as Bitcoin use a "proof of work" system to prevent abuse.
Artworks are proofs of aesthetic work.
The difficulty can be varied by altering the size and blur of the pixmap. Or by only allowing particular detected face bounds rectangles to be used a set number of times.