1) Over the years I've noticed that most players want to take the character sheet home with them as a momento of the game. I think I'm going to start putting the name of the game, the event, and the con on all pregens, as well as the date and location of the con.
2) No con/demo charsheet should ever be blank on the back. Don't make the character write-up longer than necessary, just put something cool on the other side. A map, an illo, some useful game charts, a manifesto, just something. Don't waste that space. At a con I once found a charsheet for QAGS, the Quick Ass Game System, that had the chargen rules and pretty much the entire system on the back. That was rad.