When my cousin Erika graduated from senior high school in 2002, I decided to make her a roombox as a keepsake of her graduation.
The box: I used a box intended for mosaic work; it came with a large hole in the lid. I painted the outside, turned it on one side so the lid was at the front, and covered the hole with clear plastic on the inside.

Swedish graduation customs: This room features a Swedish senior high scool graduation cap on the chair, and a collection of gifts and flowers on the table. At the graduation day, family members gather outside the school to wait for the graduates, usually bringing a poster on a stick (often featuring the graduate's name plus a childhood photo), so it'll be possible to locate one's family in the crowd. I decorated the outside of the box with blue and yellow ribbon in the colors of the Swedish flag - that, too, is often used at graduation festivities.
Credits: The chair is by Betty Turmon, the painting on the wall by Julia Sensiba, and most of the wrapped gifts on the table are by Marilyn Nielsen. The horse shoe is a bought metal finding painted black. I made the rest of the items in the room. The roombox itself is a sturdy box which I added a false wall to.

Here's the dress she'd sewn for the pre-graduation festivities

How I made the horse: Erika's education is geared towards horse care (nutrition and lots of other subjects), so I wanted to include a horse in the roombox. I used a bought mold (for a tin soldier horse) and paperclay to create the horse. I didn't have any suitable photo for the poster, but as Erika has long hair I could use a catalog photo of a Barbie doll. :-)