Hello and welcome to Pixelation.
What kind of game is this for?
The dragon looks very happy and non-threatening. The upward curve of the mouth and eyes really suggests this.
Biggest issue I find is the is lack of gesture:
Your reference piece has some careful compositional mechanics going on in it that give the dragon grace, emphasise the feeling of its movement, and direct the viewers eye along the line of it's attack, enforcing its power. Decide on a simple curve to base your dragon's gesture upon, and work your composition around that basic line.
The curves of your lines are rough, looking like they were drawn with the line tool or something. The tail is not as bad, but the wings are really jagged. Its right (our left) leg doesn't really make sense in the lineart. It's missing the connection of the "knee" to the "shin". Makes the area's planes very ambiguous.