Creativity is as important in teams as for individuals, I think. This picture is about 350cm x 110cm. It was made by 8 individuals that did´t know each other very well or not at all, and there were some rules applied to the exercise. In short they were: everyone will pick 3-5 symbols from cards, then they were to paint them all over the paper, anywhere, in any direction (the paper were placed on a table that everyone could easily walk around) The only rule was, everything you do has to be connected to something made by someone else, and you have to ask them if it´s ok to connect. It is also a good thing to share brushes and paint to save the resources as much as possible.
I´ve tried this workshop on both kids and adults and it works very well in both categories.