This is my first attempt at making something in Gimp, I basically laid down a clouded terrain with a brownish red hue using turbulence to make the land appear cracked. I used the mountains tutorial by Roba to create mountains, although I did mess up a little bit and it made some weird circular lines around them that actually ended up looking kind of cool with blending. Overall I still have no idea what I am doing, but I thought this came out nicely. I also ran the cartoonist feature to bring out some relief lines to create a sense of depth.
Click image for larger version. 

Name:	Plains.png 
Views:	454 
Size:	650.0 KB 
ID:	56765