is it a curved staircase? What is the highest point of the staircase? maybe you can do something like this image:

you are thinking about the space right now. it looks odd, no doubt. 1) when you fill in with the furniture, just make sure the three steps are hidden. 2) consider three potted plants of different height, so the rectangle is complete. 3) glass bowl with Siamese fighting fish for each step 4) figurines of different heights 5) 2inch square wooden bar on each step up to the top of the rectangle. and complete the entire rectangle if you want with a smaller rectangle open in the center my suggestion is, there is a reason why this space ended up like this. it will look great once you put something there. things like these are what make your house unique.

the design looks great . According to me one side of windows can be used as bed wall . we can have blackout curtains or blackout window blinds . You can even play with drapery to define the area behind bed. We already have seating in the room so next we can do is give a console/ study table with an puffe / chair to it. also one can add a bench at the end of bed. Size you can check on your Autocad . Bed wall should be the focus when one enters the room, so I feel the bed should be placed like this . Dimensions of furniture and circulation space you can work on. Also WC should be on the washbasin side to avoid Future leakages and dampness in bedroom wall. all the best

Jaggi, We guess that it is roughly 20-25'x 25-30'.