Cardboard and musty go together well here where it tends to be damp. I've gotten rid of most of the cardboard in my darkroom and garage and have plastic or metal containers. You should be able to get a variety of plastic containers (even milk crate style at a smaller scale) at your local dollar store or equivalent. Running a air cleaner (one with a fan, not an electrostatic one) has also helped immensely in darkroom cleanliness and air quality.