Plus, the algorithm could always use some optimization. I figure implementing a true genetic algorithm (several 'painters' working at once, recombining their DNA instead of overwriting) would get to a 'good enough' result more quickly.

It makes me wonder whether there is some demoscener who has already done something like this to fit the Mona Lisa (or probably something geekier, like a picture of Clive Sinclair) into their 4k demo.