I am the Queen of Overskirts! I love them, and make them all the time.
An over skirt is a simple piece of fabric that uses pinned layers to create "pleates". After you can fasten it over top of another dress or skirt to dress it up.
Below are a few examples of overskirts I have made for photography.
I purchased the gold lace on sale, and planned to place it over top of this particular black skirt that I had. I also made the crown out of Worbla, and hand painted it. This was from my workshop in Italy in May 2017, so I needed a crown that would lay flat in my suitcase so it wouldn't get wrecked during the travel.