Our group did a lesson on painting and incorporated an Easter theme into the lesson because we presented right before Easter.  We asked the class to paint three different eggs using a color that they found in their Easter egg before the lesson started.  The students learned about line, shape, and color.  The students were asked to be creative in their paintings and to use each of the elements we talked about.  After talking about each element, the class was given practice time to work on producing the element and work on designs they could use for their final eggs.
As an extension activity, students can use these elements to create paintings for almost any subject.  For example, a social studies project could be a poster or painting of the landscape of a certain country.  The student would paint mountains, lakes, and maybe roads using the elements of design.