Simple lessons can be packed with information. Take this picture for example, the kids are drawing a profile of a face and the also a face looking straight on. They are also learning about temperature, the blue/purple side is cool like the moon and the yellow/orange side is warm like the sun.
I have also discovered the joy of "watercolor" pencils. The kids color the picture and then we get out the paint brushes and water. When your done it looks like watercolor. It's perfect for days when the kids want to paint but the teacher doesn't feel like getting out all the paint and cleaning up a bunch of palettes. :)