(photos: martha stewart)
I would have never have guessed, but they are cookie sheets covered with fabric! How great of an idea is that? (And I love the greek key ribbon bookmark peeking out from that book.)
You can watch the how-to video on Martha Stewart's website. It's super simple: just use spray adhesive to cover the tray in fabric and then put a piece of felt on the bottom. She also had a piece of acrylic cut to size to set in the tray, but depending on what you planned to put on it, you could skip that step.
I have several baking sheets that have seen better days in the kitchen, but would look fabulous covered in fabric!