Note: I used only profile pictures that I have used that fit these descriptions, cause I've had a lot of profile pictures. Shut up, ya'll don't know me.
The "party-er" picture
Someone puts this picture up when they want to let everyone know that they are the party animal. These people are down for anything! They also tend to pass out the fastest every night cause they had, like, nothing to eat all day, bro.
Usual suspects: frat boys
The "gangster" picture
"This person is a badass" is what they want you to think. A "don't f*ck with me" face, a posture that says, "I don't care about you", and, to complete the package, some gang symbol is thrown up with one or both hands. The desired reaction is not obtained because the least intimidating people usually do it.
Usual suspect: white sorority chicks
The "majestic/epic" picture
This person wants you to think that their life is a lot more interesting than it seems. They get a lucky shot and instantly it looks like whatever they were doing before should've been filmed for a Michael Bay movie.
Usual suspects: people who probably don't get out enough
The "artsy" picture
These people want you to think that they are deep and thoughtful. These people end up looking like pompous know-it-alls that will tell you till they're blue in the face about why we have to save the White-bellied Spider Monkey before it's too late.
Usual suspects: art majors, mac users, emo people
The "I'm fun!" picture
Most likely, this person has a good sense of humor, and generally is nice person to be around. They are also known as the "clown" of the group, so you know there will be wacky high jinks when he/she comes to a party! Or maybe that's what this person wants you to think.
Usual suspects: cool people, possible loners
The "group" picture
Nothing says, "I have friends and a social life!" quite like getting a bunch of your friends together and taking a picture of it. It could be anywhere- at a party, at a football game; there really is no limit. The only downside is that you'll probably stop talking to them in about 6 months.
Usual suspects: people you're no longer friends with
The "my facebook just got hacked into" picture
This person is- hey, what the hell? I really need to remember to log off next time