I assume by "draw a picture in crayon", you mean provide a very simple explanation. You seem to be confusing the fact that children generally draw simple things, and also draw with crayons commonly. But there is nothing about crayons intrinsically that means a crayon drawings must be simple.
Having drawn with crayons, pencils, and pens, I think there is an intrinsic property about crayon drawings that does severely limit their maximum complexity/detail.
