hello; you might like this technique. (pic above for demonstration)
It was somethingng my husband used to do.
got a thick piece of cardboard
covered it with melted wax
covered wax with indian ink or any paint that won't flake
took a little ticking needle (any needle with BLUNT END)
scratched through wax to surface of card
this pic is black and red but you can do it any colour. He never tried wax crayon but it should work fine. I experimented with this and it and it is very versatile. I wish I had thought of melting down crayons!
you can't see it in this pic but he end result has a lovely gemstone look. though of course the surface is fragile and can easily be damaged there is no problem if you get it framed, as this one. He loved this technique as he found it much more exciting than painting. I wish we had thought of adding crayon to the melted wax!