Well if you want an idea of dieselpunk
Try checking out the movie The Shadow
The game take place after the end of world war 2 but world war 3 is starting to loom on the horizon when a new enemy is stepping forth out of the smoke like a child's nightmare. The streets have become crime ridden as criminals take advantage of so many people going to war.
During wold war 2 the Nazi's tried to invade the US through NYC the fought their way in land and took and held a good part of NYC. it was soon found they were not invading but looking something in the Bronx what ever it was when they found it he caused a huge explosion at one of their labs which gave the military and a group calling themselves The New Yorkers. They forced the enemy out and cleaned up and rebuilt it better then before and made it symbol of our victory but its been many years since then. A year after the rebuilding strange events seem to always center around the Bronx and resonate out. Scientists are still trying to figure out whats causing it but life must go on. The strange things going on in the Bronx has caused massive discoveries in science.
I don't want to put much more for fear of spoiling to much.
This is an alternate 1940's with more advanced tech but with a dieselpunk look to everything. Their are flying cites and many other things.
thinking the game will be a 300 point game but it can be flexible if you have a really awesome character idea.