In the photo it feels like the table should be turned the other direction. Have you tried that. I agree the sideboard is a mismatch for that beautiful table and chairs and it is too small on that wall also. Then see how it feels to you. You might not need an accent wall. I might put your lovely art on the wall where the mirror is now too. What about curtains on those big windows they would soften things up.

is an accent wall the only plan for the dining room?

Is the room/window at the front of the house?

Turn the Table

Select a larger sideboard and install a vertical mirror or vertical art and buffet lamps

I rarely like mirrors in DRs but you have agreat piece of art that really needs something to anchor it in the space so how about a longer buffet with the art abovw it then maybe some type of wall decor or even wallpaper but right now I think the seating at the table is odd , no placemets please . I agree some lamps on the new buffet a large colored bowl on the table and so drapes for softness and privacy maybe a nice silk in a color from the art . The chadelier is not one I would choose since I never like them to light ceiling and not the table and it is a bit high too. Wajt is the greenery fake or real where you plan to change often? Is the table rectangular , the pic is distorting the space maybe a better pic no fancy lens stuff .