Dieselpunk. Because steampunk isn’t dirty enough.
Apparently if Dieselpunk’s too dirty, now there’s Decopunk. First rivets, then grease, then chrome.
I usually think of DP as taking place 1920s-40s, in that crowded era when Nathan Zachary, Joe Sullivan and Cliff Secord squabbled over whose flightplan had priority, when Henry Jones Jr and Lamont Cranston bought fedoras from the same shop, (respectively: Crimson Sky, Sky Captain, The Rocketeer, Indy and The Shadow), when Nikola Tesla taught Mad Science 101 at Miskatonic U., and when the new power rising in Europe decided to go in for professional villainy first and politics second.
Outside that period, add 1984, Blade Runner and Brazil to the list, and there are many more.