Carpet is used all the time in basements on concrete floors. If you don't have any moisture coming through or don't have a flood or don't live next to a lake, then no problem. Buy the best pad and nylon carpet you can afford but it probably won't get the wear like an upstairs carpet would. At least a 38 to 42 oz carpet will be good and not cost an arm and a leg. Your local carpet dealers will tell you if there are any local reasons not to use carpet.