Nice cartoony design and colors, 'tis pretty. It looks a bit weird that his head is on fire, but it casts no light on it's surroundings (shading on the shoulders and arm should change accordingly, if you decide to do this). And maybe you could try adding a little transition between the fire and the skin on his neck.
The hand on the portrait looks broken, it's too twisted downward, and the finger is lacking a few "segments". Maybe rotate the hand away from us, or up a bit.
