The russian wildlands in the painting of Yefim Volkov (1844-1920) :
Backgrounds from Samurai Jack by Scott Wills (2001/2017, Cartoon Network Studios / Williams Street) :
Each illustration of Tadahiro Uesugi is a lesson of composition with lights and drop shadows :
More inspiration and references on my twitter account : https://twitter.com/sylvainsarrailh
Have a great week folks!