You don't want to increase the combustible load in the corridor if there is a fire in the corridor. Door decorations increase the combustible load in the corridor.
DVC has their rules about no decorations can be seen from the exterior of the resort. So no door decorations, no lights on the porch/balcony. They implemented this last winter prior to the holidays and sent e-mails to all members about the rule change.
At resorts like AKL, the doors are already decorated. Same with many of the othe deluxe resorts.