HI,
Lets talk about how and where PIcs are in the first place.
With iChat (and to some extent Messages) you add a Buddy and the service they are with send you a Buddy pic
If you Add their "First Name, Last Name" info then a Address Book Card (Now Contacts) is Created and as a Default setting the Contacts (Formerly Address Book) takes the Buddy Pic from the App.
You can Enter the Contact app (Address Book) and change the Pic for that person.
You can then chose in Messages to highlight the Buddy and then do CMD + i together to see their info Card and chose which picture to Show in Messages/iChat
The Buddy Pics from whichever service are held in:-
~/Library/Caches/Messages/Pictures
The Address Book/Contacts pics are part of the meta data associated with the Card
I don't have a Facebook account and have never synced any pics from there.
However you may have enough info to progress from here
10:06 PM Wednesday; September 26, 2012
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.2)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
Couple of iPhones and and iPad
"Limit the Logs to the Bits above Binary Images." No, Seriously