I disagree with your title - profile pictures can be very telling.  While a proper photo can show you what they look like, profile pictures tell you how they see themselves. If the subject is using tricks to make themselves look smaller, they're self conscious about being too big (prolly fat). Dude crops off his head at the forehead - he's self conscious about his hair for some reason. Long hair draped over the face - something is under there. Fatness, scar, wonk-eye... whatever it is, they're ashamed of it. Dude takes all his photos looking down at the cam - he's self-conscious of his height. Guy has no pics of himself in short sleeves, probably thinks he's scrawny. (Knew a guy who did this. He was right, very scrawny.) Once saw a photo set where a dude had 4 pics, all of him posing with his hand obscuring his upper lip. You guessed it, cleft palate. I can keep going but you get the idea.