From (what I think) was the peak of the CDmailing during the late 1990s, I had the back wall of my classroom lined with ISP CD's. My students brought them in & put them up. I had hundreds, but eventually ran out of that gooey sticky stuff that I was using...never got around to buying more.
I think some students used gum (which I didn't allow in my classroom).
I can't remember if I left them up or not after I left the school...