Check out the last question / soundcloud file here. That should give you some inspiration.
Just had a thought as I was drifting off to sleep. How can you take advantage of the height of the space? Not sure if you can get up to the top, or how good a result you'd even get, but what about unfurling a really long piece of fabric, shaking waves into it, dropping it into a pile, etc.? Dry, wet, different fabrics (try the discount bin at the local fabric store.)
Could be really cool, or it could sound like really bad foley, not sure.
This also makes me think: giant slinky.
Ok, brain expunged, sleep now.