My after school students just love making marbled paper! We started with starch and watered down tempera paint. We poured a layer of starch in the tray then dripped small spots of paint with a spoon.
Then they used shaving cream and liquid watercolor. We put these long thin pipettes I got from a lab that closed years ago into the bottles so they could better control the amount.
We also made our own comb to drag through the colors with a chunk of cardboard and toothpicks. Such a fun afternoon. I think they would make great images for note cards or ATC’s.