I personally love this rough style you use. You really know your way with the right brushes and textures, which is awesome (I still have a lot to learn about that).
It has kind of been said before, but your focal point seems to be the ship and if you detail that just a bit more, or give it some clean edges it would really enhance your vocal point and make it pop out more. The rest I would leave exactly as it is!
well, its good to try and push for a finished look; but I supposed there should be a middle ground too you know. Somewhere in between sketch and finished where you still feel comfortable showing it. That's what Im gunning for. Sketches are too vague and true finished renderings can take days, but if you manage to hit something in the 4-6 hour marker which has that rough sketch feel but is very clear then that'd be awesome