umm this is already possible with myphone... when you add a facebook photo or any other photo to a contact, all wm does is add the location of the pic into the notes field of the contact. ive hard reset several times and used myphone to restore my contacts and the fb pics are still associated with my contacts. this also works for pim backup. i hope i didnt confuse you, but basically what im saying is that the info that controls which picture shows up for a certain contact is located in the notes field of the contacts. if you go into one of you contacts that has a pic and look in the notes area, you will see what i mean.
