If you are new to the Gimp, you need to check out the Tutorial forum.

Find RobA's tut on creating an artistic regional map. This tut covers quite a bit of GimPs techniques and will help you along quite a bit. Once you start making maps, post what you have done every few days or so and we are very willing to offer suggestions as to how to improve or correct problems that may crop up. Don't be shy, cause we are a friendly bunch here and we do not torch or ridicule any thing posted. Just good friendly C & C with the creation of awesome maps as the end goal.

Follow the above advice and before you know it, your maps might be among those featured on the front page of this sight