These are also very nice clouds! Mind to share a tgc / settings?
Did you ever work out that scene? It's good looking! With a little bit of work on texturing of the terrain and rendering at higher quality it will definitely look very good!
Another thing which might also be interesting for this image is to decrease the gamma to 1.7 and increase contrast to about 0.35 in the rendersettings. Then increase camera-exposure to about 1.3-1.5. This will produce a much clearer render.
Well, let's get further on-topic
Martin