I've seen a lot of crayon art on Pinterest, mostly with just the wax running down the canvas, and occasional featuring an initial or something similar. I think it's a neat concept, so I had to try it out on my own.
The steps are pretty easy:
Get the crayons in the colors that you want separated from the rest in the box.
Use a hot glue gun to glue them in the pattern you want the colors to run in.
Use a blow dryer, running back and forth over the center of the crayons, to heat them up until the colors begin to run, and they run as much as you need them to.
Allow the wax to dry.
I decided to make a little scene, and use green and brown crayons as grass, blue, white, and silver for the sky, and yellow and orange for the sun. I also bought fake flowers, cut the flowers off the stems and glued a few to the tops of some the "grass" to make it look like stems.