You make a collage....
I made this on picscatter.com. I linked the site to my Facebook profile and then pulled the photos into the collage. For this particular one, I chose my Facebook friend profile pictures. I clicked on every single frame to choose the photo I wanted. It was kind of time consuming, but worth it for the end result. Unfortunately not everyone could be included, I couldn't choose the number of squares available... so no hurt feelings!
I have also made several scatter collages with my Facebook albums and made them my cover photo. My favorites were made with vacation albums. I think I might make a collage of my October photo a day photos. It's fun to see the month as a whole.
A big thank you to Facebook for allowing me to connect with all of these wonderful people every day...and for helping me laugh.