looking good! Making me wanna root for team fire. I believe moirae has a good point about the fire coming from the palm instead of the mouth, mostly because of how the palm is facing and the dynamic of the pose. Emitting fire is probably no easy task, and probably requires a lot of force to produce, and the pose you have hear seems to indicate more force coming from the palm than the mouth. Whenever I imagine dragons breathing fire, I imagine them having to lean into the action with almost their entire body, much like how you would have to use force handle something like a fire extinguisher, otherwise the can would fly backwards with a lot of force without a firm hold. (I hope that comparison wasn't too confusing >_<)
I also want to suggest maybe having the soldiers in the foreground cowering in fear and hiding behind their shields from the massive blast of fire to make it seem even more terrifying and dangerous. This would make your dragon even more powerful to behold!
Keep up the great work!