I was able to get a bunch of cool old keys off E-bay for a few dollars. My husband then made a Photoshop document with the shape of wings. I printed it onto "antique parchment" paper and had my son Adrian cut them out. We then taped the wings on (tedious), tied nylon thread to the key and taped the thread to the ceiling using clear packing tape.
I think he was nearly ready to kill me over this one. But he helped.
Taping wings on keys has to be one of the weirder things we've done in our life.
I got the large key off E-bay as well for $10. It was perfect and was used to unlock the door during the Golden Snitch hunt. I know the kids will continue to use it for imaginitive play. At least that's how I justified the expense. It took a little extra tape to secure.
It turned out to be a cool effect and helped make our boring basement hallway feel a little more magical for the kids.