If you can't clean up the painted edge, you could always add a 1x3 piece of wood as molding. You can even carry it up to the ceiling to frame that wallpaper. I don't see that paint color in the wallpaper, or maybe it's a lighter version of the flower centers. Maybe stencil on a design using the darker color, or another color from the wallpaper to help tie it together. Then narrow floating shelves or vertical frames or something in the painted areas it you feel you need it. Maybe turn the bed around so the wallpaper is the headboard.

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.

I have some suggestions if you are thinking budget friendly changes. Make a photo gallery with different size frames and arrange them parallel to the stairs, so you can enjoy each photo as you climb up. And for the area that will be on a level with your upper floor, try some pretty decal that will connect the photo gallery to upper level. And last, if you have budget add some beautiful hanging lights in the stairwell. Also think about repositioning your refrigerator.

Greetings From Dream Design, We have selected some ideas so that your all the requirement can fit into this --Make a wardrobe near the computer table and and put the mirror on the wardrobe handle So it will solve the dressing issue also and then you can put the queen bed and also put the side table - designer wallpaper on the bed wall -Place the curtain on the AC wall ,and take the white color curtain -put the cream color of all the wall so that it will look big -make the study table color as coffee color