Choose elements that switch-hit. Find a table that can function as both a desk and a dining table. Get daybeds or deep sofas that can double as guest beds. A storage ottoman can provide an extra perch, a little table, and a secret hiding place.
I like the little day bed and the window and beat board walls. day bed on plywood base with built in table. we would put the long edge further back for under the bed storage space. I also would want to paint it like white or something.