Is it obligatory to return pictures of Pharaohs' statues to one's father, or to destroy them, knowing that they might be a trust or a gift, and the father might not dispose of them?

Figurative statues of the Pharaohs are Haram by consensus because they glorify disbelievers and involve the depiction of animate beings. The one who makes images will be punished until he breathes life into them, and he is not a breather. Such statues also prevent angels from entering. Therefore, statues must be defaced or destroyed unless doing so would cause strife. As for photographic images, their ruling is the same as that of photography. If the images are a deposit, try to convince their owner to destroy them.