This is a pretty nice artwork for something you described as "QUICK". I love the eyes on the character and the heads of flame for the others. The flames could use more of a glow to them, less lines, more vibrant effects. I love the background, subtle but nothing plain, something to look at and admire but not look focus from your main characters. Not too much to change here and I think it is not bad but I'd add more effects to it. Sometimes simple is good, these types seem simple but theres always so much more then that, and you have shown that here with this not so simple style but more complex ideas. So my Overview of These kinds of creations are always a fave of mine, as they bring a little more to the canvus, you bring detail and you bring a new style of creation and thats what I like to see. my Extended closing notes are its different and unique.
~~THINGS TO IMPROVE ON~~
Just more effects to really improve it a bit.