This site has got quite a few nice GLSL shaders that can be adapted for use with the Visualizer:
(works best in Chrome)
I adapted this shader (attached): https://www.shadertoy.com/view/XdlGzr
The GLSL is basically the same, I only had to spend about 10 minutes renaming a few variables and some other minor adjustments to make it work in the visualizer.
Anyway, that site adds new shaders every week so if anyone finds a good one we can try adapting it.