I use mididings[1], which is a set of python bindings for receiving, transforming, and sending MIDI.

Using it xdotool[2], I've done things like used various MIDI controllers to send keystrokes, mouse movements, and mouse clicks to various applications that I use.

You could potentially use this setup to control GIMP, Inscape, Krita, or other drawing applications.

[1] - http://das.nasophon.de/mididings/

[2] - http://www.semicomplete.com/projects/xdotool/

This is pretty cool, I think in general we need more novel forms of input in computing. We've been stuck with a mice and keyboard for too long.

Combining with some of the things pmoriarty mentioned, I wonder if you could make this more widely useable.

That's great! I would like to see somebody using this solution while being synchronized with the beat of the music.