Just as klue said: you can use any fabric and any crayon. I have done parts of a quilt using crayons and I had purchased the small pack f fabric crayons. I have since learned that the good quality regular crayons work just as well.
Personally, I prefer muslin for this type of quilt.
I did a kid quilt for a teacher once, and had the kids draw their pictures and messages on on a predefined size paper. The pictures got scanned into the PC and printed on fabric. Some of the pics were not bright enough, and I colored over them with fabric markers. I used some "school=related kid fabric" as sashing and it turned out fabulously. Gotta find the picture.
Good luck.