Joseph Cornell is a great artist for inspiring creative sculpture boxes.
Students could bring their own things in for filling their boxes.
Ready-mades a la Marcel DuChamp- make them take an everyday item and change
their perspective of that item.
Robert Rauschenburg's "Combines" would be another great inspiration for
assemblage.
As you can see, I am big on art history. Our high school teacher did not
believe in teaching about ANY artists, so I was the student's only source of
that knowledge. He just retired, so hopefully, that will change!