This pic aims to do 3 things: Reference the silly storyline of the original arcade game where Marian is the twins' common girlfriend. Acknowledge some of the Western covers and advertizing for the game and its early ports which depicted Billy Lee and Jimmy as angry beer drunks and/or red necks (mullets included). And finally, the game is supposed to be set in a post-apocalyptic world, but it doesn't look like it as you play it.
The pic was made with pencils and colored in Photoshop 7. Backgrounds are a mix of direct coloring (skies and vegetation) and vector graphics (everything else).
But I ran into problem when I started shading the characters, it looked off and it wasn't something I could correct with just playing with hue or level settings. So I started over and used a simpler form of coloring and changed the light source. That explains the discrepancy between the background (if you look carefully, it's more like early afternoon, despite the color balance which had been altered later) and the characters (low sun, close to sunset).