Quoted from jwilson:You should take a spin through deviantart to see some of the artists there.
http://www.deviantart.com/
Lots of pros, lots of hobbyists, but most of them looking to do paid commissions. There's a number of other similar sites based on your budget, but deviantart is the place to find undiscovered talent. Feel free to hit me up on slack if you want to talk about it further.
DA definitely skews towards hobbyists and amateurs, for a serious project I would suggest spending some time poking around on Behance https://www.behance.net/ (lots of great illustrators) and Artstation https://www.artstation.com/ (a little more focused on 3D artists) instead.
Just don't expect any deals (or unlimited revisions), most of the folks on there are pros and expect to get paid fairly for their time and effort.
Always great to see new artists try their hand at pinball games as a canvas!