Tutorials
From Blender for Architecture
Create a seamless texture
Gimp is the only tool you need. It has two powerful filters.
- (in french) "Carte -> Rendre raccordable"
Makes a fusion of the 4 corners of the image to make it tilable without seams.
- (in french) "Carte -> Petit raccords"
Tiles your image 4 times or more so you cans see if the result looks good (without seams).