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!
CarnivalSensation February 2015
Carnival Dream November 2015
Carnival Fascination April 2014
Carnival Elation March 2011
Carnival Imagination Sept 2007
Carnival Sensation Dec 2006
RCI Sovereign of the Seas Sept 2006
Carnival Miracle Sept 2005
Carnival Glory Sept 2004
Carnival Fantasy Jan 2004