My younger girls had so much fun making the scratch art ornaments, that they wanted to do more right away.
I gave them another sheet of cardboard (this time blank on both sides) and had them color it (on both sides) with a starburst rainbow pattern, being careful not to allow any of the cardboard to show above a line I had drawn for them, an inch from the bottom of the sheet.
Then, they colored over the rainbow pattern with a green crayon. Green does not block out the colors underneath as well as black, but they did their best to get it all covered up.
We cut out Christmas tree shapes (with the blank cardboard at the bottom for trunks)...
...and they went to town scraping out designs.
They had such a good time, in fact, that once they had finished decorating their trees, front and back, they decorated the all scraps...
...leftover from cutting out the trees, as well.