The angel's right leg should be more visible; she seems pretty full-bodied until you get to the legs and then you're suddenly reminded that it is a flat picture. The same probably goes for the demon/devil/manacled victim; if he is going to be in such a position, wouldn't his legs be spaced out somewhat so you can see the other one behind it? Even just a tiny bit; he does not have to be straddling the lava flow.

Other than that, I do like it. The colors the of the sky blend well, the poor guy's butt is illuminated by the lava he sits on, and the people are generally well drawn in perspective and porportion.