Sub Lesson - Watercolor Circle Art. The results are always eye catching no matter how kids chose to paint it! (possible with markers)
Lots of Art Projects for Kids: Abstract Oil Pastel Cat, Mrs. Katz and Tush - good math lesson on fractions and geometry
Arty Crafty Kids - Art - Art Ideas for Kids - Autumn Handprint Tree by ashleyw
"Wheat Field with Crows" by Vincent Van Gogh is perfect subject for practicing layers of oil pastel.
Valentine's Day: Draw a heart (or trace), have students use rulers to draw lines across. color heart in checkerboard then outside in two more colors.