Last year, I had my 6th graders make sunset silhouette pictures with a watercolor background, and Sharpie marker (fine and ultra fine tip) for the silhouettes. The students did a nice job drawing their silhouettes, but many of them got lazy with filling them in with markers. It is fairly tedious to color a large area in neatly with a marker.
This year, I tried a similar project with my 4th graders, but after we drew the outlines of the silhouettes with Sharpies, I had them paint in the shapes with tempera. I told them that anything small could be filled in with marker, but to do the larger objects with paint. This gave much better results over all! Below are a few examples of 4th grade art.