I'd use a simpler mirror or piece of art above. If I used a mirror then I'd use colorful, taller glass vases, identical but bright. It's looking a bit contrived at the moment but it's not a tough fix.

Something different in the niche.

Lovely pieces but perhaps too busy together, in saying that I love the look of the mirrored pieces together in the pic.

Agree with others change out the mirror for a piece of art that offers color. This would be a nice place for a colorful painting or favorite framed poster. If you are determined to keep both pieces try adding interest through larger taller accessories on chest.

It might be helpful to share a photo from a project we did. Notice the mirrored surfaces in the room.

You will often see mirrors above mirrored chests, but in this instance, they are competing due to having too similar patterns. You could move the mirror to another wall and it would be fine. As the ledge is too narrow I wouldn't add anything...once you add some lovely art, that will be all that's needed in the niche area (you could add a stick on pot light to the upper ledge). The one vase in the centre feels off - accessorizing in 3's is more appealing/balanced and use high/low as well for an interesting vignette.

Can you fit a chair or two? A dark framed mirror would look pretty :)