We have linoleum floors in our house so we use area rugs... We also have two dogs, so we don't buy nice area rugs... we get the $19.99 ones and replace them 2-3 times a year after a dog pukes on them. I take them outside and clean the dog ick with a hose and a scrub brush, let it dry and keep them rolled up on one side of the garage. When I work under the car, I unroll one and use it until it gets too filthy or oil soaked to use.
I first thought that ductwork was for an A/C system that would blow across the garage floor... which would be nice here in FL. I bet a squirrel cage fan from an old A/C system would hook right up to some cheap galvanized ductwork done up like that and keeps things nice and cool.
