I'm well aware of Steampunk as primarily a literary genre slipping into computer and tabletop roleplaying games and movies etc. from there, but I haven't heard any attempts at making it a music genre yet.
My main exposure to steam punk has been through the tabletop roleplaying game Castle Falkenstein .. Some brilliant source books came with that one, like Leonardo DaVinci's sketch book containing lost sketches and other books with steampunk inventions like gigantic zeppelins looking like oil rigs suspended under giant balloons and doomsday machines for causing earthquakes. Worth checking out for those who like that sort of thing.
When I was younger, I drew my own steampunk doomsday machines (running on steam of course), I never got around to actually building one.