Enviromap V1.4 script assists in the rendering of environment maps suitable for use with GIMP's Lighting Effect plug-in. It is based on the article described here. The script uses a random seed, along with multiple user defined parameters, to generate endless variations of several types of environment maps.
Menu Location: Filters/Render/Environment Map..
Ctrl-F will regenerate the map using a different random seed. By default, GIMP's "Golden" gradient is used. However, you can choose any appropriate gradient to generate an environment map. The script supports the smooth topographical style map, as referenced earlier, as well as a cloud based map. You can select a Gradient or choose to use GIMP's Active Gradient. You can blend the specified gradient back into either style map to create some unique, interesting and useful environment maps. User selects blend mode, shape and direction of gradients.
In addition, it's useful to apply GIMP's color setting to shift the hue or saturation/lightness on the rendered map to get the desired results for mapping.
Please visit the Support thread on GIMP Chat for more details and examples of how to use this script.