If you want to find a way to generate other texture maps like bump map, displacement map, ambient occlusion map the easiest way, well gimp can do it too.
First you need to download a plugin called INSANE BUMP. Once it’s installed open gimp, go to filters – map, and you will see a new option called insane bump. In case you don’t have any idea what these maps do and what they are used for, then watch the video below that explain how these maps works in 3D using blender.
Download INSANE BUMP.