Welcome to the Guild J.A.C.! You did a nice job following RobA's tutorial. It looks like you might have used an early version of my Photorealsitic Trees technique for the second map. I've made some improvements to that tutorial that might interest you (just check out the link in my sig). There are several other great GIMP tutorials as well, depending on what style you are interested in attempting. Gidde has done a nice GIMP conversion of Ascension's Atlas Style tutorial that might be of interest. Gidde has also done a nice tutorial on a more hand-drawn style map ("for the artistically challenged") as well. You would do well to spend a couple hours just searching through all the various GIMP tutorials since there are allot of gems to be found. I wish you all the best and encourage you to post your work-in-progress maps in the appropriate sub-forums so that people can offer you constructive feedback during the map creation process.

Cheers,
-Arsheesh