Looks great! A little darkening near the base of your cliffs wouldn't go astray. I think the blending you did with the rocks looks a really great on the right side and the left would look better with the same blending. triangular shadows next to the crenelations (on top of the wall) will help show their height over the wall, though the shadows on the sand already give that information. The more important part is that you did great digesting the techniques so you can use them for your own nefarious ends.