custom raster artwork for screenprinting

I am looking for something for a customer of mine. We have an annual event in our state that she would like shirts for, which is Bike Week in Laconia, NH. The business this is for is a scenic train tour company. I was looking for a simulated process design similar to the ones you see if you google biking event shirt images for Sturgis or Laconia or Daytona. A design my customer really likes is the back of this shirt: [login to view URL] She likes the colors and the subdued quality of this design, the darkness, etc. If we could come up with something along the lines of this design, but without the puppetmaster, and with some ghost motorcycle riders/skeleton riders riding alongside the train. They use mostly diesel engines, but think people relate more to a steam engine, and they think a steam engine would look better for this design as well (similar to the train in the backbone of the railroad image).