Swatch-books are a great way to show detail in a theme. A swatch-book can document studies, and as a display of work. Students can collectively arrange and compose their swatch-books for the rest of the classroom to use.
1.) Have students explore a media, such as oil pastel or paper-cutting. You may want to use botanicals, paint, watercolor techniques or even one of the elements of art and design (i.e. balance, color, value, etc.).
2.) Display and discuss the discoveries.
3.) Cut, paste, and document the explorations into one binder so that your classroom can flip through and reference a study.
You can build entire works out of just one swatch. You may even want to collect and crop photographic prints. These prints can work as a spring-board for the rest of the classroom work, and cue everyone in on what each other is exploring. Students can then choose original subject matter and content.