This guy's perhaps not really an absolute "Dieselpunk icon" by everyone's definition, but in the last few days I've been obsessed with Claus/Claude H. Freese, who created transitional-period flying machines in the 1920s and 1930s. Previously, he had been busted for trying to sell alleged cutting-edge weaponry to the Germans during World War I:
http://revelationawaitsanappointedtime.blogspot.com/2009/09/claude-...