I would probably paint all the drywall surfaces the same color. It looks in the pictures that the ceiling is one color and the walls are another color. Pretend the walls are all standard height and hang artwork at an even eyelevel height below. I put a high bookcase in my living room and hung my pictures slightly lower than the top. I would install a drapery rod between the lower windows and the curved upper window and add draperies that go to the floor. It will cosy the space while letting your beautiful ceilings soar. Your furnishings are quite dark so I would look for a coffee table and accents in light wood or metallic to add interest and make it look like its not staged.