I would get a rug

You need an area rug and window coverings to soften up the hardscape.

side board under the mirror?

You need dining chairs that match, a side board, a large piece of art instead of that mirror, and an area rug.

I don't feel that matching chairs is a pressing need. This picture looks to have been taken at a casual moment. At other times just put the 2 non-matching chairs at the ends of the table. Yes to softness and color via art work, window treatments, rug, and just a little "stuff".

Can you turn the table the other way, put the buffet or console table under the mirror with two lamps and with the mismatched chairs on either side of the buffet/console table. Only the four chairs around the table. Rug and drapes will finish the room

I would add a tablecloth that matches flowing curtains.

No table cloth please.

What has been suggested is very nice, but to give the room some more life I would suggest a carpet with a little more color, perhaps repeating some of the colors in the painting you decide on. The purple flowers add a lot, but I think more color in the carpet will add the final touch to this room.

I will try with color. But what I learnt for myself that color all the time looks good on picture. In reality it might be different.

IKEA rug

celerygirl is certainly helping... but I think the 2 darker chairs look skimpy in comparison. If anything, larger chair at the end: sort of wingback?

To brainstorm -- here's a room similar to yours: ceiling and chairs relate -- yours with some color?

Seaside Style in Brentwood, TN Suburbia · More Info

IMO the mirror is not a good look for this room because the room requires more texture. I have inserted two framed printed & silk like drapery panels. I've also painted the walls a slightly darker hue.

If you like bench at left [moving upholstered around], a bit more visual space for 'filling the perimeter' by walls:

Lake Oswego Main Floor Remodel · More Info

.... and I partly meant having a console on the wall by the bench.... maybe painting the ceiling a soft color would accent the round/and chandelier? Do you have bench-size children?!

Actually, I like what celery girl has come up with in the post showing both the ikea rug and a blue one. Once you have your table centered under the light, you will not have much room left, and the narrower shelving adds texture without mass. Take a look at the two looks: does it seem to you that the first room appears spacious, and the second is a bit busy? That is because the first photo is monochromatic, and relies on texture and depth of colour for interest - a much better idea for your more intimately sized room.

To me, what's in the rest of your house matters: does it "lack wall color" /// or do you like a texture [or all-neutral], rather than some color.... ?

Or... do you like, have plans for pattern in curtains? A simple wallpaper looks good I think:

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Actually you do not need neither side console and shelving, you can just go with wall art.

Every time I see this question:

"What should I add to dining room?"

I just automatically think food! friends! love!

Good suggestions above; your room will get there as you start living in it :)