I am not a fan of the top down one due to the repeating texture, though it has a nice potential for a good starting place, BUT, the POVRay 3D one is super frackinlicious!!! Could you try to do a few slightly overlapping heightfields (with various overlap amounts and see what a mountain range might look like (especally the 3D version)??

Perhaps I could use this as a base and then use the smudge tool to muddy it up a bit to get rid of the repeating pattern and apply a bump map on a 50% grey layer set to overlay might work really well to have some nice foldy creases and crevasses.