I often use actions to do this and that much faster. So I experimented a while around and this is the result. An action which automatically creates the continent, mountains and a bit of finetuning. If you want to use it, go to window -> actions -> load action and choose 'Quick Mapping' from the list, after you downloaded and unzipped it. Nothing more to do than clicking on each step, it creates automatically a new document.
I don't know if it works with older versions than CS4 or other language packages than english (as it seems to be guided by the layer names). If not, I'm sorry. If it does work, have fun.
But for now I hope I get it even uploaded.
Oh, I forgot: if it says something about 'no pixels selected' in step 2, just click okay. That randomly appears, when the mountains get a bit too small.
Nice work! I got it to work fine in CS3, although I had to delete the Set Pattern commands and edit the Fill with Pattern command so it could find my Patterns folder.
I also wanted to include a forest, but the style I was going for wasn't doable with actions. It seems not to work with pathed brushes (the adjustments have not been taken over).