I think this is the wrong approach. I have been giving some thought to creating a game of this style. Art is where I don't have any talent at all so I would go to local art shows/displays, tatoo shops and look for online recommendations of local artists.
There are artists out there that have their own style and I would look for one that made up their own character(s) and see if they would be interested on working on a pinball project using their creation.
Some of these creative types would have storylines in their head to go with each character so you could pick their brain and get the theme's personality from them.
Make a deal where you pay them a set fee for the art or if the want to gamble offer a deal where they get paid per game if it ever got built while being honest and telling them what a long shot that would be.
I have some really cool ideas for playfield mechs and I would pick one or more to fit that game.