I think the position of the key light is not optimal. His horns are casting a shadow on his eyes, and causing her lips and face to be in shadow...I think it would have looked better to have the key light coming in from the left, making her a slight bit brighter, and him a very slight bit darker. Also, the reflection of what looks like a shoot-through umbrella on his "horn" kind of spoils the somber mood of the lighting...
The shiny specular highlight on that black horn just looks "fake". With her lips and facer in shadow, it kind of takes away, visually, and he's dark-eyed too...I really think moving the key light around to the left side would have made the shot look stronger.