A picture is just that, a picture, but most gender traits are not about the face, but about mannerisms, actions, vocabulary, the way you hold a beer in the bar, if you order a beer (no glass) or some fru-fru drink, how you walk, how you cross your legs, all sorts of things that make "DO I PASS" based on a photo alone a bad way to judge.
Remember, most people can guess gender from watching people walk away from them, i.e. they don't even see the face, they just watch the movement.