You divide a long room like the with furniture, rugs (if there are hardwood or tile floors) and wall art. A photo of the space in question would really help if you want more specific answers or suggestions.

Maybe paint the whole thing/wall black or a deep navy blue, trim and all so it doesnt look so cut up. you could turn those tall niches into bookshelves cheaply and fill em up with wonderful books. Then a couple of sculpture pieces of some sort you love in the top niche. Since its so wide, maybe two of the same facing each other? Like two horses facing each other. Or a pair of cool vintage brass roosters Those are easily found on etsy. Whats up behind the tv? Just another niche? Id move the tv away from that wall for sure. Could be cool just to fill that niche with neatly stacked wood (even if the fireplace is gas) just for decor’s sake. Alternatively you could fill the two side niches with wood and put books (or something else) in the lower niche Then you could finish it all off with two accent chairs like the picture above. Just some ideas, I'm no pro :)

I think in this case you need to make that wall a statement you could go the Besta from Ikea to save some money I often what to know what you would put on a bunch of shelves so be careful you don’t do shelf overload.These are a couple of ideas with Besta the nice thing is with it you can make it look totally custom just by arranging the units in different ways. I have used it many times for clients in lots of different style rooms

I would put a console table there, an acrylic one, with stacks of art/coffee table books underneath, or ceramic garden stools.