What do you do with left over crayons that have no use? This is what some of my students have made. We used the crayons to create these paintings with an impasto feel. The process was so fascinating that almost everyone in the studio wanted to make one picture.
After removing the wrapper, they held the crayon over a candle flame for a bit and worked with it. The results were very satisfying and beautiful.
A word of caution. Do be careful to supervise the activity very closely unless dealing with adults.