The room is 5.8 by 3.8 meters (19' by 12.5') with a ceiling height of 2.3 meters (7.5').
The front curtain also cover a projection screen as well as add absorbtion in the highs. First reflection is handled by broadband absorbers and some diffusion by, as you say, the media shelves.
The ceiling is treated with something called Sidacoustic, which is a cellulose based material with some mid/high absorbtion. Under that there's double layers of gypsum.
All walls are drywall/gypsum.
Floor is as seen a ceramic tile floor with area rugs for first reflection, the rugs under the speakers is mainly for "the looks".
Bass absorbtion is high up on the "to do"-list along with a turntable and RIAA. I have some disturbing, although not too bad, dips and peaks in the frequency respons below 100Hz particularly a dip at 63hz at listening position.