I don't blame you for being angry. Clearly someone who has no involment in your childs life can only have selfish BS reasons for wanting their photos on display
I'm not sure what i would do regarding the photo's short of not giving any pics out to family who have been giving him the pictures to begin with. Do you know which family member did this? If you do then i think it's a fair call not to allow them any photos of your child. It's a breech of your privacy and they are clearly going against your wishes which to me exculdes them from the privellidge of having a picture.