If you dont want to make your own you can find a variety of magnetic stickers at arts and craft stores.
I like them just for the fact it personalizes your cabin and makes it easy to find on those long hallways.
CCL Inspiration 09
RCCL Explorer of the Seas Eastern 09
CCL Miracle Southern '08
RCCL Enchantment of the Seas Western '07
PCL Caribbean Princess Eastern '05
RCCL Explorer of the Seas Western '05
RCCL Explorer of the Seas Eastern '04
CCL Destiny Southern '01
CCL Sensation Eastern '94
CCL Ecstacy Western '92
CCL Jubilee Eastern '90