Bowls made of confetti! Great recycling art project--save all those leftover paper scraps (put in small bowls at each table). Collect a bunch and have the kids cut them up; Then make bowls made from confetti.
How to make baking soda paint that fizzes, creating beautiful color mixing reactions. Add baking soda to liquid paint, then paint your picture, then pipette drops of vinegar and watch it fizz and spread and mix!
Magic Milk Paint idea from Modern Parents Messy Kids. This is another one of those awesome 'science meets art' activities for children, and you only need milk, dishwash and food colouring to do it. Looks fun :)