Well I had never seen the photo of the back of his head before, it is very interesting. It was not that uncommon for people to be photographed from the back during this time period. Or to be photographed from the front and the back in the same pose and sitting. Through my searches and collecting of my own family phots I have come accross some of people, primarily young children photographed with their backs to the camera. I am not quite sure why they did it but I know that they did.
Also off the top of my head I can think of two other pictures like this one. One is of Edward VII, his photo was taken from the front and back on one occasion. The other is a picture of Alexei's uncle Ernie with his back towards the camera as a child.