There's Naïve Bayes (although it's sometimes labeled in more explicit terms).

The problem with “unconventional” is that these works are anything but. As far as I can tell, the most of the paintings presented on the site follows a particular style. I don't think someone who is inspired to paint after watching the Joy of Painting would necessarily end up with something like this, so it's not just about being amateurish. It's also quite likely that some of the painters are anything but self-taught and have chosen to paint in this particular way.