If you’re creating a casual room, you probably know the descriptions you want to avoid: stiff, formal, stuffy, aloof, cold, delicate, fragile, pretentious. Casual implies a different set of descriptions: relaxed, unassuming, welcoming, warm, sturdy, comfortable.
Casual isn’t really a style. It’s a mood. It’s a feeling that nothing has to be perfect. If the pillows get scattered around the room, it’s OK. If books are open around the coffee table, the room isn’t aghast at the unsightly mess.