The first BG assignment I had on Venture Brothers was taking this sketch design of the Sphinx training room, drawn by Chris Palesty and creating the following tonal for the background painter to use.
Using the vanishing point, I was instructed to use the line tool to draw all my lines and fill them with different values of gray using the paint bucket. I built the BG in layers in case Chris disapproved of anything. Ironically, the one thing he disapproved of was using many layers.
Finally, Chris added the guns on the gunrack.