Artists can create far more ideas than fall trees if given the materials to do so.
Sponges can be cuyt in squares or cut with scissors into more complicated shapes.
Dab the sponge into tempera paints of any color and then dab onto paper. The design is up to the artist. Possibly, but expect to see more variety of individual exploration and expression. Pinch the sponge with the clothespin as a handle for painting with the sponges. Dab the sponge into the paint on the grocery tray.