I think that looks good. I had trouble representing the vertical cliffs too but to take a leaf out of Falconius excellent 3D map I think he got it better with the darker more contrasty nature to the cliffside than I had planned. So maybe on the shadow side darken it a lot and on the sunny side give it some welly on the highlights. My problem is that I dont have a shadowed side of the cliff on my map to show that with.