you have two giant alcoves. hanging art isn't going to cut it. how about two consoles? a console and a bench? some built-in book shelves? or maybe shelves?

Actually, this would look so much better for your set up.

move the tv to one of the alcoves, and hang art over the mantel. for the other side, do a similar built in or get a chest or a bench (maybe a bench similar to what you have for the kids stuff)

look into Ikea hacks for doing something like this.

or

even something like this would look nice. not difficult to do either.

Here's the built in bench I mentioned. it can lift up for storage. do some random photographs above. the other side holds the tv and media components, with shelving. Perfect look for what you have.

here are two simple consoles. you could try something like this with art above each one. But don't just pick some random art. pick something that means something to you and works w/your room. try Etsy. tons of artists on there.