Perlin noise is great for making pretty patterns, and as shown by this page, surprisingly easy to understand.

The first thing I did when I got an rPi with a sensehat (which includes an 8x8 rgb display) was to make a plasma type display by generating 3 perlin noise maps and crossfading to a new set slowly every second or so.

I still have it running on my desk to this day and get constant comments. People seem to find it endlessly fascinating