Can I use wood to build my apt or do I have to use drywall?

I am building a small loft style apt for my wife and me in Illinois. The building is a rezoned factory with apartments in it. I'm going to pick a wing and build a place for us to stay 'till our house is done.

I want to use 1/4 inch plywood as my main wall – burned stained and cleared looks very nice. I saw it somewhere else and would like to do it, kinda gives the room a rustic cabin look.

Do I have to use drywall on the inside walls or can I use wood paneling for the walls?