This one came to me and replaced my original, not-as-great "V" idea. And I couldn't believe that I hadn't thought of it earlier. With all the Baby and Little Einstein stuff we have, R is quite familiar with Van Gogh and recognizes some of his more famous paintings--or at least the ones used in Little Einstein episodes.
After searching on-line for some ideas in just how to do this well, I came across a wonderful blog by an elementary art teacher. At http://www.artprojectsforkids.org/, Kathy Barbro posts examples and instructions on the projects she does with her students. Most were beyond R's capacity right now but I got some good ideas.
I downloaded a few Van Gogh paintings, some of my favorites and some that showcased his hatching techinique the best. I would have liked to get R to work on the using the dots and lines to create the painting but what she did was pretty good anyway. She chose one of the Sunflower paintings as her inspiriation so we printed it out and taped it to the side of her easel. After some direction by Mom to sketch the horizontal line and the outline of the vase, this is what she created. I had to paint her "signature" on the vase like Vincent's but this is pretty much her own.