I try to avoid art under glass as the sun or lamps make it hard to see. I would suggest you get a nice outdoor scene work of art from online or a studio. There are lots of sites that sell online. I'd get something that shows colors and meaning but you have your own choices.

Lower all of your art its hung too high. Take the picture you have over the buffet and put it on the back wall, then if you want the tree art put that over the buffet.