We have done 2 different ones. We did the Mickey head countdown (you grab the colored ones at the paint dept of Home depot) write you numbers on the Mickey head and glue them to a poster board...
The other one is a chain link one where we print pixs of disney character glue them to the chain link and then tape or staple the links together.
The first time I did the Mickey head one I went all out and put a different scene from WDW for DD 4 so she could visually see different attraction at WDW. You could do same for cruise.
This trip is a surprise so no countdown. If I know how to post pix I would post....but...
Missy