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.
This puts the desk over the bed instead of under, so they're sharing floor space, but you don't have a bunk bed. The stairs and the platform have drawers in them. Compact Furniture For a Small Sized Kids Room