This Java applet lets you "evolve" images. The evolvotron application is a more sophisticated development of the idea.
Click on an image you like, and multiple variations will be generated. Initially the images are simple and you should probably just select for increased complexity. Note that recalculation may take a while, particularly as the images become more complex (indicated by the "N" count on each image). While recalculation is happening "THINKING...." is displayed at the bottom right corner and clicks on images are ignored (though you can still "Lock" an image, for example).
The "Redo" button on each image recalculates that image from the last selected image (the one with a red box around it). The "Big" button will pop up a higher-resolution frame (this may take a while!). The "Lock" checkbox makes an image immune from replacement when you "spawn" new images.
The scroll bars at the bottom of the applet control some of the parameters affecting how the images mutate. Reducing any of them produces less variation, increasing them produces more. Note that increasing them significantly above their starting values doesn't always work too well.
The "Dither" checkbox should be used when displaying using a 16-bit color mode to avoid Mach banding. It can be switched off when using a 24-bit mode.