A face is the most universally recognized object that the human brain can decode from any contour. A human child learns that skill from day 0 and for long months it is the only skill (sucking milk on instinct is the other) that lets it survive. If you look long enough you can see a face in anything. I wouldn't be trying to see faces in the puzzle picture. It is a task destined to succeed but it will not bring you to solving the puzzle. You'll see a face. And then, what exactly is your next step?