Don't worry about how tall the wall is; focus your attention at human height. One big piece of artwork over the table, about 2/3 the width of the table, would look good.

If you want to try a gallery wall and have digital image skills, you can mock up the wall digitally and fiddle with it until it looks good.

Look into local artists or art galleries. Some colleges have their own museums or art galleries.

Wall hangings and tapestries https://www.overstock.com/Home-Garden/Tapestries/2010/subcat.html

Oversized wall decor https://www.art.com/asp/search_do.asp/_/posters.htm?pathNumber=0&txtSearch=tall+art&Search=tall+art&CategoryID=g207263~e1808503&searchContext=configZ3L1_s1

Is this your dining area? If so then place the table and bench in the right location and shoot the picture again straight on. This way people can 'paste' ideas on your photo for help.

What is your decorating style, budget and your needs? Are kids primarily at the table or do you need a dining space for guests?

your table lends itself to Japanese simplicity, and it can be fun and easy to find accent pieces in that vein. But won’t work if everything else you like to have in your house is english country or early american colonial.... or do you like pop?

"Allegro" by Vintage Apple Collection, Canvas Art · More Info

Also, if you were willing to paint part of the wall , you could do something like this, in whatever color tone you prefer

Antico e moderno nel cuore della città - Progetto in corso · More Info

A bold and vibrate wallpaper would be nice on that one wall for a decorative effect. Perhaps one that is more mural-like than just a repeating pattern

Agreed. I like wallpaper idea. Or even some wainscoting or molding.

The only issue with wallpaper is that once it's up, you still have a large space that you'll probably want to fill.

There are some interesting small scale murals that can be less expensive than large scale art pieces.