Raised bed/planter/fence/privacy screen: this is now featured at http://www.instructables.com/id/HOW-TO-BUILD-MULTI-USE-RAISED-BED-PLANTERS-WITH-PR/ with complete instructions for building a planter with a back 48"H. You can get a PDF too. Please vote for me in the "Outdoor Structures" contest. Thanx!!
Patio screen and bench. I would paint a design or words in large letters on the back...too much of a wall to not decorate. Would look great under an arbor or other structure meant to sit beneath. Use to create a screen in the garden too. So many ideas.