I would start looking for art you like. I don’t think you need much there and it should be pretty flush to the wall - nothing that sticks out over the head of someone eating at the table, like shelves would do.

It's hard to say for sure without seeing the space on either side of the table, but I would probably put one piece of art on the right side and nothing on the left. Or you could probably do two companion or complementary pieces, with one on each side.

My personal preference is original art, which you can find in galleries, Etsy, eBay, and art fairs. Or you could check places like Home Goods, World Market, Pottery Barn, art.com, etc.

Also, and you didn’t ask about this, but I would add some color to your table. Maybe a color from the art could be pulled into the table....a lower vase, a pretty bowl of fruit (if you like to have it on hand), something seasonal, etc.

How many people eat there on a regular basis? If just one or two people use it, you may wish to reduce the number of chairs you keep there.