I think that would be cool if members can bookmark the pictures they like (with Pro Gallery). Then, in their member account, they can access a specific page where each picture they bookmarked is showed (also with Pro Gallery).
I personally would use this feature so members can easily find their favorite pictures right when they log in. They don't need to go there and there and then search for that picture in the middle of many other pictures... you see what I mean, right?
Thanks a lot. Take care.