So in an effort to avoid more of this
We did this
Rich clipped up strips of brown postage wrapping paper to the wall. (We purchased a huge roll of it at a craft store for $3.)
How long do you think that paper stayed up?
Anna had a grand time ripping it down. Threats of time out went in one ear and out the other. I should note that Em, who hadn't been up for long from her three hour nap, did not participate in the ripping. She played in the mess after though.
And yes, we have the "washable" crayons but I can't seem to scrub the black one from the walls.