Photo Collage For My Parents 25th Anniversary Party

I am throwing a casual 25th anniversary party for my parents at a local park. I have asked family members to gather photos of my parents throughout the years, but I need suggestions on how to decorate a photo collage to display. I`m going to buy a large mountable poster board, but I was wondering on where I could get ideas on how to actually decorate the board itself. Please help! Thank you. =)