J.F.
A friend just recently went to a graduation party. They had taken the professional school picture (large I think) and then adhered the picture of the first day of school to it. Then hung them on a clothesline for display.
Other ideas (that aren't so creative):
*put them in a box for your child to use as they get older for projects, their own scrapbook, etc.
*put them in a box and store at a family member's house in case of fire at your house
*put them in a box to use for graduation -- already organized and sorted!