Research

Thanks for the post about the character design Tim, this is an exciting idea! Also, Moebius, yes! Blueberry is amazing too.

On the gangster side of things, here's some stuff we can look into (written up from sketchbook):

Films
Chicago
The Godfather
Public Enemies
Some Like it Hot
The Big Heat + The Big Sleep



Art styles
Art Deco
Art Nouveau
Bauhaus (Paintings on walls etc)
Precisionism (Paintings on walls etc)