Can you use magnets to decorate cabin doors?

Are the cabin doors on the Liberty magnetic?

No, the doors on the Liberty are not magnetic, but they are metal. So yes, magnets will stick to them. On our last cruise, we used Fun Tack to put decorations on our door. It's a putty-like substance that sticks to most any surface, but does not ruin the surface or leave any residue. You should be able to find it at most any place that sells office, school and art supplies.