This script is nother in a series of planet makers. This one makes a banded gas giant. There can be anywhere from one to 20 bands in the planet. Each band is an equal height, and has Plasma noise rendered in it. Each layer is then motion blurred. The result is then mapped onto a sphere, and gaussian blurred to make the edges nice and fuzzy. The resulting planet can also be rotated to any angle, and the saturation of the image can be changed to make the colors either more pale (for more realistic looking images) or more vivid (for the cool factor.) The higher value noise you use, the more grey the planet will turn out. Between one and four seems to be a good number.
The final size of the image can be anywhere from 300x300 to 3000x3000, and this script works with Gimp 2.6.0