Surfing through the wallpaper section of freshmeat, I found a reference to the "de-jong-explorer", a fantastic program.
It basically renders images produced by some simple formula, the Peter de Jong map equations:
x' = sin(a * y) - cos(b * x) y' = sin(c * x) - cos(d * y)
This formula has chaotic behavior for most values of a, b, c and d. The author has put an image gallery of some pictures online: navi.cx/images/chaos.
It quickly installed and a small program, try it out!
NP: Pearl Jam—Black, Red, Yellow