John Carlson in his Guide to Landscape painting talks about starting a painting with the big "poster shapes". In Carlsons day silkscreened and showcard posters were very common. They were in stores and posted as advertising every where. Here are a couple of posters from that era so you can see how they looked.
These posters were silk screened, a way of mass printing that was popular for graphics in those days. Silkscreen printing lends itself into large shapes of flat color. That is the look that Carlson was referring to when he spoke of the big poster shapes.
Below is first that poor painting again and below it, my posterized version.
When I designed this little painting I reduced the big shapes to a handful and bound them together in value groups. I minimized the different values with in their big shapes to unify them into larger areas of a nearly singular value. Essentially three big darks and a big light shape.
I have posted on etching before and will probably pick up on that thread again. The etchers, particularly those in the 19th century did this particularly well and I have studied them a lot to get ideas. The Japanese printmakers used this kind of arranging too. Here is one of those, by Hiroshige.
Arrangement of simple flat decorative shapes is a good way to organize and plot the design of a painting.