Both this year and last year we decorated our front doors for Halloween. The DS had a Halloween decoration kit with Mickey bats, ghosts, paper lanterns and paper pumpkins! This year I found removable double sided tape tabs designed for teachers to use in classrooms. It works great for the paper type decorations and leaves no residue when removed!
I too would hesitate using any type of decoration or fastener that would require extra Mousekeeping or Maintenance to put the unit back to "original" condition. After all, we all pay for upkeep out of our dues and I would want to make someone else pay for my decorations when they don't get to enjoy them! As for lights on the balconies, I brought lights, but after thinking about it, I decided to hang them in the room and not out on the balcony. It seemed that they would take away from the "look" or "theme" of the VWL and also intrude on others view of the outside.