The mirror should be 2/3 the width of the cabinet. With that mirror I would say the cabinet should be wall to wall there. But art would be better because there is nothing worth seeing twice reflected in the mirror.

The pieces don't look centered on the wall, but that could be the angle of the camera.

Install a chair rail, wall to wall, just slightly above sideboard. Wallpaper, wall to wall, under the chair rail. That should help balance the mirror. Then on either side of the mirror, add a sconce.

This is helpful, thank you!

Good...don't leave the chair there. Match the smalls to the wallpaper you choose. For instance,

Consider painting the frame.

If I tried to make the shelf longer, for example, bought another kallax shelf (2x2) put it next the the 4x2, would that work? Or would that look wonky with the extra legs etc

Sorry but that mirror is not right for this spot. Might be good as a vertical mirror in a bathroom or bedroom. The cubby unit is nice. Yes, remove that chair. Put a collection of 4 prints above the unit. And switch up accessories on top. This is casual but functional entry set up.

Ok, also fyi this is in an indent wall, so it’s like this area is framed

I saw that. I couldn’t do the mock up exactly but I think my concept can work well.

So plant on one side or both sides?

But on left for plant and keep it wispy. Olive trees like this are perfect.

You don’t need to fill every space. You could put a small basket on right if you need a spot to drop shoes?

I'm going to guess this is a dining room not an entryway according to the light reflected in the mirror and the dishes in the buffet. So you won't need a basket for shoes. I think I would move the chair, center the buffet, add a lamp, and replace the mirror with a smaller mirror or art. Wall paper would look nice if you choose to use a mirror.

Ok. If this is in dining area still can work with your bar tray set up too. I do think a lamp would help in this niche. I would also add a book or two in the cubbies to elevate your display pieces so the are different heights. Turn books so the pages are facing into the room not the bindings. A picture of the space and other walls from further back would help from here too. Thanks. You

Cool idea! Thank you

@Flo Mangan, table lamp or lamp stand?

Table lamp. Size and shape depends on art somewhat so I would pick art of choice first. Without more pictures of the whole space it’s impossible to be sure.