Pastel art with a watercolour and salt wash, the ideas are endless. Also this site has lots of fun classroom art ideas. Do this with the Native American legend book "Thirteen Moons on a Turtle's Back".
October art - Draw pumpkin, grass in pencil. Trace all lines with glue. Next art class glue will be dry. Watercolor page with splotchy painting. When dry, trace over glue lines and splotches with sharpie.