Added thanks Keith
I find after you have the wallpaper you want, you need to resize by unlinking the width x height options. then set to size you want to a square(remembering when the globe is created, it shrinks the WxH bay a half. Example: Wallpaper 500x500--Globe will be about 250x250).
The wallpaper will look stretched, but when it becomes a globe, it will look normal again.
Also make any needed conversions(color mode, sizes...) before creating the globe then just make one and export as gif, selecting Animation.
As I said it is good at making planets. It's one of the things I still use GIMP for.