I'll be glad to paste my DIY RPG-style diffusor plans--one and two dimensional--into an email, to give you a quick look at them. Aesthetically acceptable? Not for me to say, but my wife is willing to see them as modern sculptures. You'll need serious bass absorption too, I'm afraid, to overcome the room modes associated with your square room. A recent idea on that comes from Bob Riggle, former Arcici designer who has a fabulous isolation platform, by the way. He's made something like an Argent Room Lens with 4" PVC tubes joined at the bottoms to form an 180 degree continuous tube, and he says it absorbs (in Helmholtz resonator fashion) down to 30 Hz. I haven't tried it yet myself.
My email: nicetom@sonic.net
My email: nicetom@sonic.net