Steampunk is generally considered a kind of alternate historical fiction - a past-that-never-was - primarily focused on the Victorian era, when steam engines on trains and ships were the height of technology. It supposes that the switch to electricity either never happened or simply didn’t replace steam power, and that machinery is composed of clockwork and gears. In the book world, some consider it a subcategory of science fiction, and some place it on its own shelf. It is both a literary genre and an artistic aesthetic, as you may already know, and its influences can be seen in fiction, film, TV, music, costuming, high fashion, accessories, and of course, jewelry.
Costumers, historical reenactors, and fans of all kinds have found that steampunk allows them to be as decadent, as imaginative, and as unique as they desire. A steampunk costume can run the spectrum from a museum-replica Victorian gown, to an airship pilot in a leather jacket and grease-tinted goggles, to anything in between, as outlandish or as minimal as the wearer chooses to be. Steampunk is a fantastical feast for the senses, and includes extraordinary working mechanisms, as well as artistically placed gears and wires, and can be based both in history and in the imagination, in equal measure.