from Mike Hergaarden: As for generative art in Unity, the easiest approach would be to use the built in particle system, there are a lot of exposed settings. Particle physics etc are all possible.
However, also still very doable is to use a spline controller to have objects move along a certain path: http://www.unifycommunity.com/wiki/index.php?title=Spline_Controller (Suggested here http://forum.unity3d.com/threads/58994-Drawing-Generative-Bezier-Curves?highlight=generative+art )
Then another topic highlights the use of Metaballs and Voxel Skinning: http://forum.unity3d.com/threads/76165-Voxel-Skinning?highlight=generative+art
Unitys procedural examples: http://unity3d.com/support/resources/example-projects/procedural-examples
I'm skipping the details of the previous subjects for now as I remember an article that might be a great resource:
Shiftcontrol is (was) the company that has been doing a lot of generative art in Unity. They once wrote a short article in a Unity magazine that has only been around for 3 issues.