stored in address book but retrieved by opening address book
"It is part of the addressbook.
So it's in ~/Library/Application Support/AddressBook/Images/ "
The pictures should be stored in this location but I was not able to retrieve mine. One quick work around was to open address book itself, go to my "card", click and drag on the pic and drop to a safe location. Repeat for each account picture you want/need to retrieve.
Cheers!
ECC