One of my favorite art activities is called "Cooperative Earths".
Children do this
in pairs. Each paints a paper plate blue. Then 1 of them puts 4 "smooshes" of green paint on their blue plate. The 2nd child puts 4 "smooshes" of brown paint on THEIR plate. You can add little dribbles of white paint if you like.
THEN, you put the 2 plates together, paint sides together, rub a little bit, then unpeel them. They turn out to be beautiful representations of the Earth, as seen from space. Very impressive around a bulletin board.