Here's a quick sketch I did to experiment with style & texture. I drew it with pens and a black Prismacolor pencil on canvas paper so that I could get the graininess of the paper to show up. I added the zip-a-tone look and spatters in Photoshop and then laid down some flat colors to finish it up:
This closeup shows the texture a little bit better:
My inspiration to try out these new (to me) techniques came from several sources. I was looking at some movie posters from the '50s when they started using more graphic styles (like this poster for Vera Cruz), also some of the illustrators of the same era who were experimenting with looser rendering techniques (like Mitchell Hooks here), as well as a contemporary comic book artist named Dave Johnson who uses a lot of these same inspirations & techniques but gets a very modern feel out of his work (like this cover for 100 Bullets).
For as little time as I put into it, I like the results, though I need to see if something like this would work on sequential pages. It might be too abstract to look at page after page.