Okay so, there really is not much to say. In actually a lot of this is style and design prefferenced. You could do whatever kind of feet or wings or teeth or whatever you want. I will only really point out what I think should needa little work.
The skull and jaw you drew was very loose and the jaw definitely a bit too curved. You kind of want to stiffen that up and give it a nice strong jaw shape (of course if you want go with an abstract plant/shadow dragon thing, then by all means throw that advice to the wind and do what you want, but I am just talking in the precense of the generic scaley winged lizards here that are mystical but still are bound to the laws of nature... and bones)
Your drawing was a little squished for my tastes, so I definitely went with a longe more roomy body. Detail can be your best friend, or your worst enemy, but even the smallest lines to seperate nails from tow or teeth from gums can really help. The wings could definitely be larger (if it can fly, some dragons have small wings and dont really fly). And the flames could be alot looser and curvier, especially at the ends. Any details I did add or mess with were purely just prefference (Like the ear and brow line and nose point, I was going to add scales but HAH, no thankyou)
I hope this helps you, I had fun drawing it (up until the feet lol, excuse the ones on the right side of the body, they suck). If you ever need any help or advice or something, feel free to pm me! I would be happy to help you out.

