styrofoam covered with fabric wall art. My daughter and I did this for her room. We used cheap painter canvas and scrapbook paper. We sprayed adhesive glue to the canvas and layed the scrapbook paper on top.
Something like this in the front room. (Different colors) Plywood, Painters tape, and different paint colors. I can't wait to see the look on people's faces when I say, "Yeah, it's just a little something I threw together one day while bored.