When I was growing up, my parents turned our living room into our play room. They just had an old couch and table in there, and everything was crappy so we could do whatever we wanted. We ended up getting glue, glitter, paint, etc. everywhere.
We don't have room for a playroom here, but if we did I'm sure chalkboard paint would be involved, and a lego wall. Maybe we'll just have to incorporate these things into LO's room when she's older.