Don't know if your aware but I have a free utility to create terrain a lot like this. It has a mountain pointyness factor which you can adjust to get more or less low lands. Not as nicely colored tho but I am sure you can create a height map to color palette transform which would give the same.

http://www.viewing.ltd.uk/cgi-bin/vi...nstant_islands

The little app creates a color and a greyscale heightmap. This link gives a free 3D viewer for it too. http://www.viewing.ltd.uk/cgi-bin/vi...dragons_flight you could use it with your terrain too if you have the height map for it.

Your sig says 100% photoshop but there are some characteristic streaking on the map which makes me think that its something else...