Before I retired, they disallowed shaving cream for us.
We used to make the most beautiful pictures using shaving cream, marbling food coloring through it, placing card stock upside down in it, patting it down as to collect a lot of different colors, then taking a straight edge and 'shaving' all the extra shaving cream off. They were always so different and made gorgeous cards.
Another thing the dcks used to like to do was marble painting. Sometimes I'd get ambitious and cut the paper into a shape that signified something seasonal.
Sponge painting, stamp painting, potato/apple/celery printing
Then a favorite was supplying lots of different materials with glue and let them create collages.