Sarah, I would paint it red, or black, like your art; as in, go with it.

Or, move that furniture out and do what this upper photo shows; keep it white or paint it black and make a table over it.

I'd put an umbrella stand to the right of it, and then I'd hang my art to encompass the whole wall, whether with one large or two offset smaller prints. Mock-up in a minute.

not my best, but gives you an idea, anyway:

What about floor mirror? Just make an angle so it a little away from the radiator.

Use an ottoman or bench under a console tablle. Hiding the radiator while layering and giving visual interest to your wall. Do not look at style but inspiration to show you the idea. Best of luck.

Ask the property owner to please remove it if it is non-functioning, or ask them if it's OK for you to remove it? Use it to hang winter scarfs, below it, a basket to the right on the floor for gloves, umbrellas and hats during the winter. Maybe on the right side above the basket, one of those wooden coat racks that attach flat to the wall. A mirror and lamp on the table would brighten up the space and you can check your look out as you leave the house