It looks like potentially a really cool space! I think the duvet is fine, unless there are stains or something we can't see. I'd nix the dust ruffle or anything frilly, and try for a calm and restful oasis - a pretty throw in a soothing color would be fine, though. Guests will appreciate a place to put a suitcase, so if the vanity is going elsewhere, maybe a folding luggage rack, chair, or small dresser. For the bathroom, I think you should lose the floral wallpaper, ottoman, and butterflies - again, calm and restful, unfrilly and tidy. The neat angles and architectural shapes are the main story here - you can work with them or against them.