If you are concerned that with minimal display you won't have enough color in your room, choose items that are colorful like the flowers or the pillow on the chair. This is a simple idea for corners. Fill a vase with tree branches. These are cork screw willow branches. They help to fill the corner, but they still look simple.
Scale is important.
Large items will look less cluttered whereas a bunch of tiny items can produce a cluttered look. You don't have to gussey up every focal point. This fireplace is simple but still remains the focal point. 1 reason it will always be the focal point are the bricks. The texture of the bricks will stand out from the white plaster walls.