I vote for bedroom/study.

What do you think about the color. It's a Ben Moore paint. Very dark. Should I lighten it? Here is my other rooms.

What furniture arrangement. Thinking white sofa

Here are other views

I really like the idea of a study, but is that something that you would use? I think you may have pulled the dark colour of the room from the floor? I would use this colour on the ceiling and then pull one of the gold colours for the walls. It will give you a very cozy feeling.

Guest room/study.

I do think I need to either paint another color or do wainscoting to break up the browns of wall and floor

I love the idea of a study/library. I'm picturing a Ralph Lauren theme with the current dark walls and wood flooring. Leather furniture, plaids, paisley. Have fun!