As far as decorating doors...I have a set of mouse ears that I put around the round room number door sign to create a mickey and I would be willing to share with anyone interested..just let me know. The doors are magnetic so I buy self-adhesive magnet tape to use to put it up from a Michael's, AC Moore or office supply type store..
Also in the general cruise thread there is a door sign thread where people post their pictures of their door....
basically anything works...some people make signs for each day...you know port of call pics, mickey and minnie in formal wear, disney pirate stuff for pirate night, anything with your family names, personal celebration pages commemorating a birthday, anniversary etc.....
It can be as simple as the Home Depot Mickey Head paint color sample cards with your cabin member names on them to VERY ELABORATE...I will say most of them are computer graphic designs...Check out the door sign thread. I got most of my ideas from there...of course I forgot my signs at home

on our last trip..
I also made matching family shirts...with iron-on computer transfrer paper designs on Tees from Michaels. It is a cute and relatively cheap way to start your vacation celebration and it looks great in the embarkation pictures!