There are some fun ways to use a crayon that make interesting designs. Try these ideas:
Notched Crayons
Have an adult use a table knife to cut notches into the edge of a peeled crayon. By rubbing this crayon on paper the children will notice the effects of thick and thin lines.
All-in-one Crayon
Take 3-4 crayons of different colors and tape these together. Just make sure the points are aligned. The children will enjoy using this rainbow-colored drawing tool. Think about taping together red, yellow and blue in hopes that when the children combine these colors they will discover secondary colors of orange, green, and purple when the colors overlap. You can also make bundles using thick crayons for a varied line width.
Crayon Swirls
Just remove the paper from the crayon and show the children how to hold the crayon on its side and twist it around to make a swirl design.
Pointillism
This method is also good for showing children how primary colors can look like secondary colors. It's an art method where you place points (dots) of two colors together and it appears to look like another color from a distance. For example, when filling in a section of a tree, the child can make dots of blue and yellow together and looking at the picture from afar it looks green.