Family face book pages or groups are great for sharing old photos as well and current photos and information. You can put whatever level of security you want on it – whether anyone can join, you screen who joins, anyone can post, or posts are reviewed by you before posting or no one else can post. Your call.
To make a family page/group interesting – try to have posts a couple of times a week at least. You can preschedule posts so that they are posted on a person’s birthday for instance.
You can also post pictures and brief biographies of ancestors (see above picture)
This kind of page is great for sharing old photos and identifying who is in the picture!
Posts with pictures engage more people.