I have a very large piece green wool carpet, size 13x16. There are a couple of vent cut-outs along both long sides, making it more like 11x16. I got it via ebay in never-used condition. I have had it on my floor about three years. These older wool rugs tend to mat, but it's in pretty good condition.
I have a second piece of grey olefin carpet. 13.5 x 14.5. It is free also. It has been in a bedroom for 10 years. Could be used to keep dust down in a storage or shop; Could be used in a bedroom too.