The GNU Image Manipulation Program, or GIMP, is a raster graphics editor application with some support for vector graphics. ​more...

Get the GIMP

• Linux: ​official Webpage or as package in your favorite Distribution
• Windows: ​Installer (don't forget to install GTK+2 too)

GIMP Texturing HowTos

• ​very simple metal
• ​rusty texture (I hope we find a better one)
• ​marble
• ​making a texture tileable

… just a collection of tutorials… not evaluated yet!

other GIMP HowTos

• ​Planet creation script

Other HowTos (not GIMP specific)

• ​Texture Tutorial - How to create a tileable texture out of a non-tileable texture
• ​tilable texture (photoshop)