I think you did a good job on this one. As a commission I think it's hard to really create something truly original or visionary. From my perspective this is a very cool, kind of sinister take on eastern drakes with a flair of western in the horns and more mainstream fantasy in the overall appearance. I think the tongue is a bit thick, I feel like it should have been more serpentine and less monstrous.
In relation to the growth of your artwork, I would certainly say your are getting a very strong identity in your style. I have found myself saying "that looks like her style/work." So bravo on that. Hope you have found this helpful, if something specific is bothering you I'd be happy to look more closely at that.