hmm. I’m sorry this post is so late, but this was in the finished work at the mattepainting.org and I had to sign in here for this… (and stand that 24hours message validating for new users) 
This is a great image, but it seems to have something disturbing. These are just my opinnions and critics is given only because I know you could do better. :twisted: Previous entry to the Legends “Hall of the Dragon Mist” is still one of those inspiring images I look from time to time.
Imho that the rock is the issue - on the other hand it makes this interesting, because it is different, but on the other hand it’s difficult as it is now. When thinking about the composition, it seems to be quite huge element at the center of the image (and as you said earlier - there is almost nothing). I have hard time taking my eyes of from it and the ship, which is quite short distange for eyes to travel in the image.
If the background story is about the gulf, safe haven for the pirates - I would like to see the gulf, let my eyes travel slowly in the curved shape of the coastline and notice all those details while traveling. Now there is the Rock (and the ship). So one suggestion is that the rock could go or be considerably smaller (not cutting the water -area in half). Then you could also remove the tree from right fg and maybe crop a bit from left. Even the ship could be flipped then (returning home from the battle?). Composition might be easier to look then (but maybe also more tradiotional, if not boring?).
The other option might be to make that rock worth looking - fill it with staff you could imagine in secret pirate haven - disguised lookout towers, a light beacon than could be seen only from one direction from the sea and cannons which could smite anyone who is (un)lucky enough to find that pirate haven…
And the minor points…
- saturation perspective looks quite fast from the fg cliff’s orange to center rock.
- from where is the ship coming from? Only dock we can see is at the righ fg - so just hanging around at the gulf? :twisted:
edit: and sometimes I have a big mouth. :shrug: