Go to Home Depot, get a 4x4x8 pressure-treated lumber cut into squares, sand down edges, adhere with wood glue, paint black/red/grey, adhere together, put wall mounts on back, hang on wall above the tv
If theses walls could talk...wait...they can! When guests visit, I wanted to have a fun way for them to leave a little message behind. So I painted the sheetrock walls with black chalkboard paint.