I originally posted this on Facebook as a note. I'm just curious if any Grailers have seen the same thing or, maybe even better, completely disagree with my hypothesis here. :) Much love!
I have a thought about Facebook photos that may be completely off, but a quick look through my friends list and what I know of them seems to indicate a good correlation.
In selecting profile pictures for Facebook, people are generally aware of how the picture is used. The profile picture is the face most people will see. When they comment, update their status, or upload a picture, this is what people will see. Thus, people will choose a photograph that they feel represents themselves ideally - in other words, they choose a picture that reflects how they want other people to see them. This includes people who choose pictures that are not of themselves or include other people in the photograph. They consider whether the photograph is "artistic", emotional, serious, happy, whether the eyes are looking at the camera, gesticulations, etc. This is the FACE or FACADE.
The timeline banner is different, however, it reflects inner nature. The banner picture is only seen when a person makes an effort to see it, either by going to the profile page or by hovering over a link to that person's profile page. Thus, the banner is much more likely to accurately reflect a person's true disposition, rather than just their outward disposition. This tends to be a reflection of SELF IMAGE.
What is striking to me, is that this seems to indicate and reflect strongly the relative extroversion or introversion of the individual in both their outward disposition and inner life. For example, my profile picture (green screen, eye contact, gesticulation, big smile) is highly extroverted, but I almost always choose VERY introverted banners. If you take my theory as fact, you would have been able to deduce this fact, but that is my disposition. I have an extroverted attitude when I engage others, but I tend to have a highly introverted inner life that I do not share with the great majority of people I encounter. Others, true extroverts, tend to have extroverted profile pictures and extroverted banner pictures (banner pictures that cause INTERACTION with the viewer - such as large groups of people, messages, parties, things that reflect a disposition towards interactivity over intra-activity). Strong introverts choose double introverted pictures (introverted profile pictures, less gesticulation, single subject, often "artsy") and introverted banners (art, symbols, and landscapes are all common). More interestingly, there are a large number of "mixed" types, but the trend in those is extroverted profile picture and introverted banner with rare exceptions.
Personally, I find this all very fascinating because it correlates well almost all the time with what I know of my friends when I analyze the profile/banner extroversion/introversion relationship. There are few that don't fit well and some that are difficult to judge as "introverted" or "extroverted" pictures, but on the whole I find that it works. Maybe a real psychologist will do a study on it one day.