You can set your dieselpunk story in Gotham or Metropolis, Librium or Antarctica. You can build the most incredible structures and fill the streets and hangars with every kind of weird machines. The sky is the limit! But you need something more: the atmosphere. No matter how optimistic you are, the genre simply cannot do without a bit of darkness. Stylish darkness. So, what about Noir?
We won’t bore you with academic definitions. Just two quotes from a highly readable TV Tropes article:
The Anti-Hero is the most common protagonist of the Noir — a man alienated from society, suffering an existential crisis. Frequently portrayed as a disillusioned, cynical police officer or private-eye and played by a fast-talking actor, the Anti-Hero is no fool and doesn’t suffer fools gladly. He faces morally ambiguous decisions and battles with a world that seems like it is out to get him and/or those closest to him.
The setting is often a large, oppressive city (filmed in dark and dusky conditions to create a moody atmosphere), with Mexico often playing a big role. Familiar haunts include dimly-lit bars, nightclubs filled with questionable clientele (including, the Gayngster) whom the lead may intimidate for information, gambling dens, juke joints and the ubiquitous seedy waterfront warehouse. At night in the big city, you can bet the streets are slick with rain, reflecting streetlights like a Hopper painting. Most of the characters (including the lead) are cynical, misanthropical and hopeless all the way through the film, and never find true redemption.
Peter Lorre in ‘M’ (1931). Director: Fritz Lang
Desolation. Suspense. Dark air electrified with danger and sin. Shady spots lost between back alleys. Strong drinks and heavy smoke. Dim lights. Charcoal coats and sharkskin suits. Black gunmetal. False friends. Ladies you never can trust… Don’t get paranoid. And if you do, remember: even paranoids have enemies. They are following your steps. Now!
Dieselpunk Encyclopedia 