I know there've been suggestions around the threads here, but could someone put up a list or a few choices of nice DIY fabrics to use for building panels? And some definite "stay-aways from".
Seriously, breathable is good. Not as important for in front of treatments as in front of speakers. Things like Burlap or a lightweight Muslin work well - but neither are flame retardant - most cloth isn't. You'll need to treat it.