To me this seems too close to a possible real colour-space to be properly considered a duotone - surely that wall and that forehead aren't shades of the same colour? And indeed, whether or no they are, the point is perhaps that they don't appear to be. A fairly interesting image though - perhaps a touch more visible an eye might really have pinged the impact? - certainly good enough to have been properly toned.
I dont really like the composition / pose on this one maybe if the eye was looking straight up or a bit more of the face was visable but the way your model is looking right a the wood isnt working and it makes it feel like the eye was cut off