This is great, the lighting effects are nice and the anatomy seems well in proportion besides a few quirks. The composition is nice too, I like how you have the dragon at that angle and the sunlight coming from behind. The clouds are also well done but maybe could have used a bit more definition or you could have showed more sky to make the effect greater. For me this could be greatly improved simply by adding more shadowy area in certain places, like underneath the horns on the side of the head, (not a huge shadow, just a small one to show some perspetive) The nek spikes are well drawn and very nice, but you have a slight issue where they do not follow the middle of the neck, the spikes lower down would not be as visible here (unless they curve down the side of the neck then it is fine) You could also improve this by adding more variation to scale size, it must have taken forever to draw all those scales and while I can appreciate that it does little to enhance the picture, maybe adding a few lines of bigger broader scales to the arms would help too. I do loke the way you have drawn those belly scales, they are extremely beautiful! The head is looking great too, great fierce expression and angry daemonic eyes, slight issue with the anatomy though, that lower jaw is a bit too big, (unless the dragon has an underbite?). Also, that ball where the jaw bone is, it looks odd as being the only part of the dragon with no scales on it.. and also needs to be higher up, it looks like the jaw is dislocated. Your webbing of the wings is great, I love how you emphasised transparency in certain placed where the membrane is thinner.
Thats all I can really think of right now, hope I helped you a little! (I may sound harsh but when critiquing I know you really want to know what you can do to IPROVE your piece, not so much about what is already good, amirite?)
The horns and detailing of the scales are very nice and the chest plates are very beautiful, the light coming from behind is reflecting off the character in appropriate places, just his/her neck is a bit lumpy, the front of his/her throat has a bump on it that looks out of place, so does the back. Thankfully it's not TOO exaggerated, otherwise it would look like his/her head was about to fall off from the weight. The tongue looks like it's blocking the dragon's throat and the wings are not very detailed. You could have done some more work there. The eye of it looks too small and confused. Otherwise, this picture is absolutely brilliant! Well done! 4.5 stars for vision, it looks very realistic. 3.5 stars for originality, I've seen some like this before, but you added a few bits and pieces and made it your own. 2.5 for technique, you could have easily made it more detailed here and there. 5 for impact, the minute I saw this I thought, "Oh my god, I must find out who drew this AT ONCE."