Inky, very great piece you have here! Your skill shows through and your attention for detail is admirable.
However, one thing that this piece, and many great artists suffer from is an effective use of contrast. When shooting for realism, which is generally the purpose of a good matte painting, you need to think “what defines realism.” How can we define what looks real… well, for that question you have to confront “what looks, what allows us to see?” Obviously, this is our eyes, and so, to understand what makes things look real and how to make something look real, we have to understand how our own eyes work. Our eyes work very similarly to cameras. And these two things; our own eyes and photographs, are what define “real” to us. What defines our eyes and cameras is the ability to adjust to any given lighting situation. Our eyes have censors that send information to the brain. (I’m sure you already know all this, but I’m trying to apply it!) White is always white in our brains and black is always black in our brains, what adjusts is our pupils and how our eyes recieve the light, not how it’s interpreted to our brains. So our pupils dialate according to any given lighting circumstance to achieve the most efficient, broadest range of values our eyes can handle. Our eyes can never observe every value there is in nature in any given scene, there will always be detail in the darkest of darks our eyes will read as black and there will always be details in the lightest of lights that our eyes will adjust as white. If our eyes could read the entire range of values presented in nature, we would see images similar to the one you are presenting: You’ve got incredible detail in the darker portions of the scene as well in the lighter portions, one of which has to go or both of which should be toned down. If you have an LCD screen you can instantly see what I mean, look at your image from an angle and you can see the dramatic dynamic difference a little contrast will add to your scene. Our eyes could not look at this scene in real life towards a lit sky and an unlit, shadowed land and observe detail in both. Play with the levels and curves a little and I think you will agree. It will also give a little more interest in the monochrome of heavy blue tones of your piece. A lot of matte painters and painters in general suffer from this wanting to have detail in every nook and cranny, so they do so at the expense of values and realistic contrast and values. Play around and see if you like it, I’d like to see the results as well! great job and take care
you stuff awesome … as usualy 
Thumbs up!!! can we also see the reference pleeease??? (if you don’t mind of course):D:D.