If you wanted to go all out...have Fish Extenders made for all of your guests and waiting on them when they arrive to their rooms.
I love christmas ornaments...they can pull them out every year and remember the wonderful time they had at your VR.
Candy bars with a personalize wrapper that has your VR information and/or cruise info/pic on it.
Something fun for when they get off at the different ports. Shovels, beach balls (deflated), etc. for
Castaway Cay.
Music CD
Calendar
A "Bear Necessities Travel Kit" with things like travel size tooth paste, lotion, bandaid, cable tie for FE, hand sanitizer, travel size wrinkle releaser, breath mints, emory board, travel size tissues, lip balm, shout wipe, safety pin, aspirin, tums, rain poncho, etc.
A "Bear Necessities Excursion Kit" with sun screen, rain poncho, hand sanitizer, band aid, aspirin, tums, tissues, etc.
You could give them travel games. I have a cute mickey's printable "battleship" in my 4shared. You can print them, laminate and include dry erase markers. You can come up with a fun "scavenger hunt" for the ship and include your VR in the hunt.
Customized Mint Tins
Frame for cruise photo
The list is endless!!!!
Check out the "what do you make thread" for more potential ideas:
http://www.disboards.com/showthread.php?t=2179996
Also look through here to see what others are giving:
http://www.disboards.com/showthread.php?t=1219607
http://www.disboards.com/showthread.php?t=1980639&page=15