I hate when builders leave those niches. I agree with Hallett, have a contractor build them out flush with the wall below. If you need the extra storage space, you could frame the one over the walk-in closet with doors of some kind.

Decorate the space with green silk plants (ivy) across with framed photos or vases, etc. in front. It will perk up the room.

I also hate when builder's do this. It's not even dustable - who dusts drywall to a place you can't reach? LOL. My current place I made sure the builder didn't do this. Maybe enclose the top area to store seasonal items, with doors?

Frame it out for doors and use for off season blanket storage.

Her Master Closet · More Info

I would have both walls extended to the ceiling and open one up from the master closet side for extra storage. The sloped spare bedroom isn't worth trying to use the space.

No fake plants! Nothing can grow in that dark space, so they will be even more obviously fake. And dusty.

Extend the wall up to the ceiling, as the builder should have done in the first place. Easy.