You could paint the back wall of the niche a blue or gray pulled from the fireplace? Or use a piece of wallpaper -

Is there a small light at the top of the niche.? If not that's all I would add.

I'd streamline some of your selections in the rest of the room.

In addition or instead of painting the niche, you could add wood shelves inside allowing you to use a few smaller pieces instead of just one large one.

I wouldn’t highlight it that much.
I’d just decorate it with art and a vase of flowers.

If you’re wanting to accent it, I’d look into tile, wallpaper and or shelving.

Our former home contained several statue niches. They were favorite features We rotated pieces thru them and decorated seasonally. Contrasting darker backgrounds were to highlight displays.