This topic is designed to help inspire or guide the development of MODS by discussing the various forms of Steampunk Sub-genres:
BOILERPUNK | The blue-collar answer to aristocratic Steampunk, incorporating the experiences
and hardships of the workers actually shoveling coal to bring steam
to the upper classes.
CLOCKPUNK | Clockwork technologies replace or supersede traditional steam power.
DIESELPUNK | A heresy in which diesel fuel and nuclear power replace steam power in alternate histories that often have a political component.
GASLIGHT ROMANCE | A mainly British term for alternative histories that romanticize the Victorian era. Some Brits would argue that all American Steampunk is actually gaslight romance.
MANNERS PUNK | Fiction that may or may not be deemed Steampunk, in which elaborate social hierarchies provide the friction, conflict, and action of the narrative, usually in the context of endless formal dances. At parties. In mansions.
RAYGUN GOTHIC | Although not strictly a sub-genre, this type of retro-futurism based in part on art deco and streamlined modern styles has been used for a variety of science fiction settings, usually in movies. Coined by William Gibson, the term has become more useful in the context of Steampunk as the fiction has come to feature more and more tinkers and artists.
STITCHPUNK | Fiction influenced by the DIY and crafts element of Steampunk. with a prime example being the animated movie 9, in which cute Frankenstein doll-creatures stitched together from bits of burlap sack try to save the world. In a wider context, Stitchpunk emphasizes the role of weavers, tinkers, and darners in Steam punk.
Source: The Steampunk Bible: An Illustrated Guide To Imaginary Airships, Corsets & Goggles, Mad Scientists and Strange Literature (2011), Jeff Vandermeer with S.J. Chambers
Positive there's missing sub-genres. Hope this helps.