One cruise we strung battery operated lights (although ended up moving them to the balcony), glitter pipe cleaners and something I can't remember on the door and in the mailbox. Another cruise had a red, white and blue duct tape Carnival ship (don't ask, my son was into duct tape at the time).
On my recent sisters and daughters cruise, I made big door posters. One that had pictures of all of the sisters (I'm one) both current and when we were little. The other was pictures of all their daughters, both current and little.
People would stop us in the hall and try to guess which daughter "belonged" with which mother!
And yes, it makes your cabin much easier to find after one too many drinks!
Carnival Elation March 11
Carnival Imagination Sept 07
Carniival Sensation Dec 06
RCI Sovereign of the Seas Sept 06
Carnival Miracle Sept 05
Carnival Glory Sept 04
Carnival Fantasy Jan 04