Alternatively, I noticed several photos that included no faces at all. Six of the fifty profile pictures did not clearly feature the user's face and one of those six didn't even feature a person but a crude marker drawing of one. Omitting one's own face from the profile picture defeats the purpose of the profile picture. It is meant to show others what you look like. What else, then, could people be doing with these pictures?

I can find no logical reason behind this, so I must assume they do this to look cool or mysterious. They want to use the profile picture to create a feeling or figurative "image" for themselves at the cost of an actual image. 

Below is the drawing one of my friends uses in lieu of a profile picture. He looks nothing like this. I'm fairly certain he does not have a city on his head.