Here’s a noise generator made in Processing which creates cloudy-looking noise which tiles! It’s extremely inefficient, but the algorithm looks really neat while it’s working!
Here’s a sample of its output, manually tiled (and scaled) to show that it’s seamless.

Click to start/pause, and press the M key to toggle the shape it uses to generate the noise (circle or square). When run as an application, it saves the images it creates to the sketch folder.
Tags: Processing