Re-importing photo from facebook
its better to use Facebook realtime update https://developers.facebook.com/docs/graph-api/real-time-updates/v2.2

create your callback to handle this and register it with real time updates

do the following in your callback

1- load user from facebook ID you get it in the posted from facebook 

2- get the new image from facebook

3- replace it with the current image 

4- save user

or you can forget about real time update and replace the image whenever user login

here the code you can use 

1- Make your action by Implementing hook_fboauth_actions().

2- use hook_user_login to call the action you create which grab the photo and update it 

Thats all