On a real pumpkin, let the children draw funny faces with washable markers. Then wipe the, off with a damp paper towel and draw again. My children love this and will do it over and over again.
First, go out and buy several packages of white dryer hoses (the kind that goes from your dryer to the vent outside.) Count out 9 rings on the dryer hose and cut it with a strong pair of scissors. Fold the cut dryer hose around so it looks like a pumpkin and staple the two ends together. Let the children paint their pumpkins with orange paint. Finally, make a stem from rolled up brown paper bags.
Cut black construction paper to fit inside a round cake pan (or you can use a square or rectangle pan and cut a circle out later). Place the paper in the pan. Dip a marble in white paint and place it in the pan. Let the children tip the pan back and forth so that the marble rolls, making a paint trail that looks like a web. You can sprinkle it with glitter while the paint is wet. My preschoolers loved making these. We also glued a plastic spider to the webs. This works great for a Halloween or an insect theme.
For this, you will need one milk jug (with lid) for each child. Put orange tempera paint in each jug, screw the lid on tight and shake it until the jug is covered. Remove the lid and let it dry. Add black construction paper eyes, nose and mouth to the outside of the jug. You can also let children use yellow paint to simulate a light on by painting the inside of the eyes, nose, and mouth. Screw the lid on and add a green construction paper stem to the lid with glue.