Hey! I've discovered a new play toy, called Genetica from http://www.spiralgraphics.biz.

These are some of the seamless backgrounds I've made.   These are only 256 x 256, but if you download the FREE Genetica Viewer you can render them up to 1024 x 1024, plus change the scale, hue, saturation, brightness, etc.   The Genetica viewer comes with over 100 pre-made textures.   And all 14 gtx files for the tiles shown below are in this 63K zip file.