Commercial Artists have been using photography as a shortcut ever since the camera first became available.
Lets face facts, drawing a human form from scratch is tough and time consuming.
If you are an artist looking to bang at three covers in a week so that you can pay the mortgage and have some money left over for the ponies, you will take a few shortcuts. Even the famed Alphone Mucha, who was a key artist of the art novue craze used models and photographs to help him with his illustrations. It was only a matter of time before photographs were used instead of art on the covers of paperbacks. This image is a transition. Obviously using a photograph to start with, but if you look closer you will see that the airbrush was used extensively.