I'm a big fan of collaborative art-making as well as the visual of lots of little things making a big thing. So here are 3 ways I've incorporated those ideas in projects my students have made recently.
The art club finished their "Dale Chihuly" inspired "chandelier" by combining all the tissue-paper papier-mached "snakes" into one splayed mass. I hung it in the stairwell, and have heard all kinds of comments. Usually it's, "WHAT is THAT?!" The only trouble with this kind of collaborative work is that the individual pieces can't be redistributed back to the students to take home.
I think collaboration is a vital part of learning about art. Students feel more connected as a class because they are working toward a greater goal. Every person's contribution is valuable. Contemporary artists often work in a collaborative mode, and therefore students get to experience working methods of artists today in an authentic way. As a teaching artist, I also feel that my own artistic voice is expressed with that of the children, which is very fulfilling.