The antique piece doesn't really work for me unfortunately. It doesn't seem quite right in scale and character. Think I would suggest a larger piece with doors on the cabinet. The doors don't have to be solid but could be glass or pierced metal. Instead of a mirror I will suggest shelving that could hold glassware. Honestly you could buy a hutch of some kind that would give height to the alcove and could provide bottle storage on the bottom and glassware on the top.

The mirror is scaled well to the antique bar. It needs to be rehung higher. Try putting the center of the mirror at nose/eye height. You can use some newspaper to make a mock up circle to adjust the height. Start with the mirror center at 5 feet from the floor, adjust as needed.

A tray with glasses, seasonal decorations, or a pair of candlesticks would look stylish.

Would you be willing to wallpaper that niche wall? I think your mirror would work then, plus dramatic sconces are a great idea.

Can you show the whole room, please? Is it open to any other rooms?

If you can stand back further, to show a sense of scale, that’d be helpful.

Love the idea of adding wallpaper to the space.

Not sure if this helps but the living room is open to the dining area and kitchen. I took the first photo from where the front door is. The other wall is brick and a staircase. @jilly

so I'm not suggesting you load up your bar top with all this stuff but just showing some organic-type bar decor. If you are going to do major sconces that will influence all your minor choices-- but like I said, just showing you

https://www.wayfair.com/kitchen-tabletop/pdp/cohasset-gifts-garden-glass-28-oz-wine-decanter-jnx10099.html?piid=

https://www.wayfair.com/decor-pillows/pdp/large-feather-decorative-bowl-13-x-8-clrb1847.html

https://www.wayfair.com/kitchen-tabletop/pdp/wrought-studio-daaniya-handmade-marble-black-wine-glass-set-of-2-w010551322.html?piid=414336297

not exactly biomorphic but I happen to like it with your bar and mirror

https://www.wayfair.com/decor-pillows/pdp/godinger-silver-art-co-salento-rectangle-marble-brass-bowl-rxk12028.html?piid=

Thank you! It helps a lot. Wow, great-looking house, love your flooring and brick.

Seeing the whole room, it looks fine to me, other than maybe raising the mirror a bit, as apple_pie_order suggested. I don’t think sconces would be a good choice in this case, especially as you have a set on another wall nearby.

I love art, so would want something here:

If you‘d like extra lighting there, a small lamp would work. I have a lamp on my bar cart and use it often for ambient lighting.

So now that I see how the niche is located in the relative to all the rest of your wonderfully low-key organic and simple decor, I'm pretty sure what I would do is go to the website Spoonflower and pick not only a wallpaper that I like but get a drape panel to match it. The matching drape panel would go just on the left side of the window. I'm pretty sure I would go with something dark but not flashy. Now that I see your organic look, I'd stick with organic.

I would skip sconces, but maybe have very tall slender candlesticks (really tall).

And I would not put any more art around.

So I'd hunt around but here is the direction I would go with wallpaper behind the bar and mirror and a matching drape panel

https://www.spoonflower.com/en/wallpaper/12226369-herbal-dandelion-meadow-rustic-boho-navy-orange-blue-by-milatoo

and one or 2 tall candlesticks

https://www.wayfair.com/decor-pillows/pdp/latitude-run-metal-tabletop-candlestick-w011379312.html?piid=470165517%2C470165505