Quick and easy. This is how you turn a photo into a patterns with GIMP

GIMP also lets you create seamless and artistic patterns from photos. The interface takes a little getting used to, but once you're over that hurdle you'll find yourslef feeling increasingly fond of the clever little GIMP wolf.

The Fast Option: The Seamless- Maker Filter

Far away from the sewing machine, seamless all-over patterns are often used for website backgrounds and surface textures on virtual 3-D models. This is reason enough for programers to have created a GIMP filter that lets you create seamless repeating patterns from photos with one click. You can find this option under Filter > Map > Make Seamless.

The trick behind this feature is the blending of the photo's borders using fading-transparencies and fuzzy image edges. This really is a perfect tool for doing something creative with photographs, but for making patterns from hand-drawings I suggest using the Offset function, explained here. Use this simple trick and GIMP's offset function to create a seamless repeat.

On the Gimpusers site there is a great tutorial on how to get a seamless repeating pattern without blurred edges with just a couple extra manual steps.