A Yin-Yang is all about finding balance within both side, the black and the white. You managed to put two demon in and still kept the original yin-yang shape, that's really impressive. In closer view, the balance is a bit off. The black demon contain really impressive detail but the white side is really plain. It would make the picture more balanced if you put in some detail on the white side too, rather then just letting it looked like a skull.
This is by no mean a 'flame', it's just a suggestion in which I hope to help people with improving their art by stating what I think of the piece.