This makes for a really cool design!  I gave my kids different colors of paint with little spoons in them. They scooped the paint and put it all over their pieces of paper.

Then we took plastic wrap, put it over the top and let the kids squish it around (they loved that part!) You can either take the plastic wrap off or leave it on like I did for a cool effect — you will just need to tape the back to keep it in place!