An HTML5/JavaScript port of my friend Mars Saxman's C program Starfish to generate beautiful, tiled, procedurally-generated background images. Try it out here!
StarfishJS (like its C predecesor) is Free/Libre Software, and is licensed under the GNU GPL (version 3 or later).
If you want a little peak under the hood, you can see the individual image-generating algorithms at play: the generators currently available are Coswave, Spinflake, Rangefrac, Flatwave, and Bubble.
The image generators all operate in monochrome values, and translated into color later. Some of the generated images aren’t displayed directly, but instead are used to hide/reveal pixels of other layers.