Well, everyone was wearing lanyards with their nametags anyways. Take a few volunteers, clip on some blank paper, and some tape, give participants their cards and viola - your interactive activity works, gets even more people involved, and not a sticky blue mark on any wall.
Not optimal you might say, but you never know when you are working in a space with apparently precious walls, the famous carpeted walls, or even no walls for that matter (how nice would it be to do your session under a big tree?) Give a good workshop designer a parameter in advance and with a little creative thinking they'll design for it. Everything is possible...