The mountains are very similar to how I usually do 'em. Render some clouds (Photoshop) then with white as the active color: Select > color range > fuzziness = 128 (or as much as 192)...this then selects the lightest half, copy this onto a new layer. Image > adjustments > gradient map = black to white. This puts some black into what was previously white and light gray but adds more white to the lightest pixels, put a black layer under it then merge the 2 layers then run the lighting effects filter. Delete the blackest bits, hide the layer, then repeat the whole process but with the fuzziness set to 64 or 32. So what I'm doing is to actually make mountains 2 parts, like stackable blocks...the first part creates the lower half, sort of like a flat mesa and the second part creates the peaks. Then some layer styles and colors to finish off.