This is an easy and fun project that your guests can have a hand in. They'll love viewing photos of your graduate growing up right before their eyes and you'll love revisiting the handwritten notes from family and friends.
The process is easy. Add a large mat to your 16x20 collage to allow for guests to leave notes. This example shows a 24x30 frame which is big enough to allow for ample mat board space to write messages using thin Sharpies or other permanent markers. You'll want a smooth mat surface and may need to have a custom mat cut. Remove the glass and place it beneath the matted poster which will create a nice sturdy surface to write on.
Display prominently with a variety of colored markers for your guests to see and sign. This example shows the frame displayed on a large easel but hanging the frame on a wall is probably easiest for folks to sign. Have fun making memories!