The key to a theme is the details, according to the book. So I took the idea of Back to School and brain-stormed those things that meant back-to-school to me. I bought a lot of pencils.
I bought a set of cork place-mats in Ikea for £2.50, and cut them to size: just short of the length of a pencil, and the width of 20 pencils.
Then I stuck the pencils in place using a glue-gun.
And, because they talked to me, I glued some of the empty pencil-boxes together too.