Idea 1, for the long walls. This idea would be flopped on the other wall (so where the treatment is up on the wall, opposite it would be down, helping to kill the paralells and still leaving some of the room sound...
External image, not preserved — original: http://noisefreedesign.com/studio/build/sketch1.jpg
Idea 2, for the short walls. Basically same thing..
External image, not preserved — original: http://noisefreedesign.com/studio/build/sketch2.jpg
Idea 3. This is the ceiling. As shown, the black is the MDF frame of the clouds (which are already built, have lights built into the corners). The red is going to be 2" rigid, wrapped of course...
External image, not preserved — original: http://noisefreedesign.com/studio/build/sketch3.jpg
Aside from the floor to ceiling 4" bass traps in the corners...That's what I have so far as my idea of treatment.
NOTE: All treatments would be 2" rigid fiberglass, wrapped in fabric, hung 1" off of the wall