My Bachelor thesis work - Procedural textures C library plus GUI tool. GPL.
Example tiling textures:
For convenience I've included precompiled binaries in the bin subfolder.
You can download some generated textures over at opengameart website.
Some videos:
Some Windows and Linux binaries can be downloaded here: https://www.dropbox.com/s/5xl0999w2wp0tcf/pt_designer_win.zip?dl=0