Thank you for the comments everybody, there are a lot of good suggestions here! I agree that the stones look out of place at the moment, I'm planning on using flow masks from WM, but getting a nice looking result is proving troublesome; from the camera POV they tend to appear very straight and unnatural, so I'll have to mess with that...maybe even try different erosion seeds. I have plans for isolated patches of trees and shrubbery in the mid/background, but nothing to lush since it is Iceland after all.
Thanks for looking, all!