This should have a very basic UI screen where you place the image.
it has very simple guide and rules of how to take your picture to unsure
level of quality is maintained.
This is very easy to do and I think it will be a nice feature.
Also, face detection is a cheap process today, and can be implemented
to avoid people uploading non facial images.
It can also alert if the image is not placed correctly inside the masked area.
This can maintain a decent quality of faces across the servers.
The attached image show a fairly complicated UI, the UI itself can be much simpler since it won't take into account the ears and the shape of the head.
only the eyes nose and mouth location, not mesh shape.
Also one frontal image should be enough, there is no need to side images.
Game Face, a similar feature used in EA fifa 2013:
http://www.youtube.com/watch?v=pdG8CDicD7A