AARRGH I just wrote up a ton here and it deleted..
Anyways, I wanted to say, it's really good! The structure is great; but watch your twinning (see how the legs are almost mirrored of each other) If you have them overlap then it would be dynamic.
If you wanna bring this over to the drawover paintover thread, I can doodle up some pose options for you to consider. And help you with keeping that dynamism, because, for example, the back arm being straight like that breaks the rythm of the piece and makes it static.
The fire may look shoddy to you because real fire, especially when it moves, has gaps on the inside, and a flame will dissapate at the top when the fire starts to go out. The fire, aside from the flames near his hand, aren't following the movement of the body, and that's why they may feel out of place for you.
I'd like to see what you do with it once you fix it up, though, so I really hope you post so we can see your process and what you feel is the right approach.
I think your style, colouring, and anatomy are great, but there are a few choices you can make to turn this into a stronger piece. Try and think about silhouette, for example, and just colour over his whole body in white and see what you "read" from that pose. If you show that whited out picture and ask someone "what does this look like he's doing?" and they say "I don't know" or they say something else that you weren't going for, then it's time to revisit the pose and try something new.
Hope this helps! I'm excited to see new stuff from you!