What to do with the space on the wall?

Looks clean and modern. How about some modern architectural salvage? A mirror? Blown up photo of a favorite pub or bar?

I think a mirror the width of the bar would look good.

You could open the space add shelves and a wine rack

Consider changing the wall color right there and use any of the previously suggested ideas or Google shelving and find black inexpensive shelving that has a shadow box effect. This is mine in a bedroom. You can turn these in several directions and as you see they are not going to stick out far from the wall. Change the paint bc these will show the wall

I would frames Dollar Tree mirrors, or get light weight unusual shaped mirrors from a hardware store and attach them to the wall with Command Com strips.

I would paint an accent color. Put library table against wall with short round lamp and maybe a stack of three antique books. Nothing else, keep it clean ans simp,e

Move the bar

I am a fan of an accent wall color like some suggested and some word art would fit nicely in the space.

Add a medium sized decal. You can find hundreds online and at craft stores. They are easy to apply and can be removed.

I like the sit relax and enjoy Decal .

To me, the bar looks to be in a strange location. I would put a room divider or a lovely tall plant in that spot. Looks too tight for bar especially close to a stairway.

I like Kelly's idea of the accent wall color. Wallpaper is coming back in style and you can add interest to that space with either that or paint.

I would add a nice green plant to the bar on the left side in a ceramic or metallic vase for texture. Then add a shelf with a front lip on it and stagger different sized and different wood or painted pictures frames. You could use a mixture of colored pictures or to keep with your theme you could use black and white family photos. My son and daughter-in-law did this with family photos in a small area and it looks beautiful. They used a combination of colored photos and black and white. When I did mine I used all black frames and all old family photos in sepia and black and white for a crisp look. Good luck!

I would vote for a retro type mirror or maybe a floral arrangement.

Wall mirror

Move the bar...its in a very odd space in what looks to be your living room?

A vintage neon bar sign would look great.

Is there a closet on the backside of the wall? If not, you could cut into the wall for shelving or more storage. Mirrors on front side. Perhaps even glass shelves and glassware.

I think a few small mirrors would look great above the bar.