could this be an older Amy staring through the window?
River says to Amy ‘never let him see you age’ so maybe the Amy in the picture was with Rory in the room, but she knows that the Doctor is going to come into the room so leaves so he won’t see her, but really she is there hiding, and this is why the old Rory is shocked too see (the young) Amy, because he has been with (the old) Amy for many years and forgot that (the young) Amy see’s him OR in the picture, Rory is already dead and she is just living on her own, because on the gravestone it said Rory 82 and Amy 87, so she lived 5 years more then he did (they where in the same year at school, therefore they must be the same age)