I'm not a big fb user and haven't got a clue what's going on here!
Briefly, I received a friend request from a total stranger, which was obviously a fake account.
I deleted the request, but before I did so I had a nosey look on this person's friends list.
I clicked on one of the profiles, then their actual profile pic and was shocked to find that my personal photos came up, with an option above to 'upload another photo' as my profile pic 
I came off that profile and had a look on another of the fake accounts 'friends' profile and the same thing happened again!
I then looked through all the friends (not many) and there is two other random profiles which also bring my photos up if I click their picture.
Have I been hacked? ... I really don't know WTF is going on with my photos