I would have cropped it to rectangular format just below the centerline to eliminate most of the foreground boulder. This would balance out the rocky foreground with the distant sky and horizon. It is a wonderful shot with lots of possibility.
Yes I would agree with "mts" comment. I would crop off just below the the top of the lower shadow oh the RHS. Try it on the screen by placing a card over the area to be cropped and see what you think.