Pass the hat is always a good one. Each time someone finishes a page they pass the hat. Periodically througout the night give a prize to the person wearing the hat.
Another fun game is when you have a list of photos. Call out something from the list such as a child in pool, a grandparent, a photo with flowers, etc.
The person that shows you the photo fast enough wins a prize.
Those are just a couple I could think of real quick:)