Hey there, hi there, Amy!
"You're as welcome as can be" to planDisney. It's great to hear from a fellow stateroom door magnet aficionado. This is a subject I'm thrilled to delve into!
To be honest, I haven't yet had the pleasure of sailing aboard the Disney Treasure. That opportunity will come for me later this year, and I can't wait! But I have sailed on the Treasure's sister ship, the Disney Wish twice so far. I had to "Dig a Little Deeper" for this one. But from my observations, while sailing on the Disney Wish, and phoning a few friends, it seems that the doors of the concierge staterooms on the Disney Treasure are made of metal and many magnet decorations successfully attach to the door.
Tony's Tip: Some magnets, particularly those that are often created with the help of an inkjet printer at home or similar, may not have a strong enough magnetic field to self-adhere to stateroom doors. It may be useful to also bring along some stronger neodymium magnets to place on top of the sheet magnets to make sure they stay in place. Stronger magnets like those often allow attaching decorations to the concierge stateroom doors of the Disney Dream and Disney Fantasy that have a thin wood veneer on them. I recommend using a small piece of fabric or some other appropriate cushion between those strong magnets and the door to prevent any unintended damage to the door's finish.
Note that the room number placard on the stateroom doors of the Disney Treasure are not the same round, porthole-shaped plaques of the original four vessels in the Disney Cruise Line fleet. Instead, on the Wish and Treasure, the room numbers on the doors are oblong shapes, almost rounded rectangles with lovely filigree ornamentation on the top, bottom, and sides. Decorative magnets designed to complement the circular room number plaques won't look quite the same. But I think that all of the magnets are still cute and fun regardless. Even the Disney Vacation Club member magnets that we found welcoming us "home" on our stateroom doors of the Wish were of the rounded variety. They functioned quite well for us and were a welcome addition to the collection of magnets we brought from home.
You've got me excited for our upcoming cruise, Amy. I'm heading to rummage through our storage room now to find our collection of door magnets. Besides the Disney Vacation Club magnets, we have various Disney characters, holiday magnets, magnets to commemorate previous cruises, and even a special planDisney magnet! For our upcoming cruise, we are celebrating a daughter's birthday. So we'll be sure to take along our celebratory magnets and other stateroom birthday decor.
I hope you have a magical cruise, Amy!
~Tony