Allow the use of a stereoscopic picture as the face source.

With a stereoscopic picture, you could "rotate it" a bit, to make it fit the picture better. I also found the suggestions for photo505 and faceinhole interesting as a comparison. I would recommend making your software "guess" the face and clipping much better (as it does in photo505) and then providing some colour gradient tools so that the face merges better with the background... without recolouring the who face.