Today I've spent some time playing around with this new technique for backgrounds. This one is fun (and cheap) to do!
In the first picture, you can see step 1: simply colour with crayons onto a piece of paper (I used sketch paper). You should colour quite heavily. After that, crumple the paper quite thoroughly. Then I painted over it with a coat of black acrylic paint, which I then removed (before it dried) with a wet sponge (or you could use a wet papertowel too). The paint will remain in the 'cracks' that were formed when you crumpled the paper. The results are shown in the second picture.
The next step is to let it dry and then place it between two sheets of paper (I used a couple of pieces of printer paper) and then iron it, using the low setting on the iron. Picture 3 shows the atcs I have ended up with. The 4th picture shows what happened to the piece of paper which was on top of the crayon batik when I ironed it. It, too, is a fun background. Hope you try this!