Most garden fungicides (the organically acceptable ones, at least) seem to use various copper compounds. They wouldn't bleach the rug, but some copper compunds can be toxic (something John doubtlessly knows from using copper carbonate and black copper oxide in glazes) and they may stain.
Sulphur is also a good natural fungicide (high sulphur content is why strong onions keep far better than sweet onions) but I've only heard of using elemental sulphur, not sulphur-bearing compounds, and elemental sulphur STINKS.