Wonderful job with your color selection! They set the mood of a heavy storm perfectly! Also, fine job with your light source/direction. The only thing that could use improvement is the wing tip on the left. All the rest of the dragon, even the other wing, has more detail put into it, yet the wing on the left is colored in a way that it comes across as flat. Having looked at a couple of your other pieces, I know you can do better.
Oh, great work with your background! Having the clouds as a subtle border around the dragon, and leaving an empty space directly behind it is very well done -- no distractions, or conflicting lines! Keep up the great work!