Cool room, first of all

I'd do couple bigger paintings/other type of art, maybe a bit assymetrical even, and you can do leaning and overlap them a bit, if you wish, in the center/a bit to the left(my left lol)..and I would try to put some bigger books on the other end..not sure about shelving, unless you do it so high you can hardly reach it...add a bookend, a plant, favorite sculpture maybe-done. Don't take the whole ledge, give it some breathing space. You can place smth like a small foot stool/tray table/chest next to it, on the side below and put there some books as well. A big basket, next to the sofa..

but if you have a big collection-you'll need to account for it and find another spot for the rest of the books

I love books myself, it's not some huge collection, and I have a sort of dedicated library, yet they're still everywhere and overflowing

I love them being everywhere..but I understand your desire to not clutter fireplace too much, I like its proportions now, one should be very considerate as not to mess with them.

I would do larger pieces of art above the mantle. I've seen some beautiful examples of layering art and thought it might be fun to try with your mantle.

There is absolutely no reason you can't have bookshelves above the fireplace unless you use it a lot and the heat will damage the books. But whatever goes in that space, it has to be big and bold. One shelf will get lost. Four (two on each side) will not. I would go with an art wall, although not my best art if you use the fireplace because again, it could get heat damaged. Large metal or pottery sculptural pieces could also work. We use our gas fireplace for heat, I had to rethink my habit of putting candles atop our former non-working fireplace. They all melted.

One caveat: I am a dyed-in-the-wool bibliophile, so I'm always looking for ways to "decorate" with books, i.e. find places for my large collection. That drawing looks groovy to me, with the understanding that I would not put my best books up there due to the heat, but perhaps the heat would not be an issue since folks routinely put their tv screens above their fireplaces now and I have been told that's not an issue with it damaging the works. I might mix the books in with some larger art pieces. I also have a rather large pottery collection which I scatter throughout my living and dining spaces too. And a collection of pictures . . . But that's just me, ymmv.

I might also go hog wild with some type of artsy fireplace surround, like a giant peacock or nature motif. Again, just me, I like pattern. https://www.neimanmarcus.com/imported-painted-fireplace-screen-th.html

I feel your pain. I got rid of some very artsy decorative teapots that I never, ever used and even less now that I have developed a health problem where I can't even drink it if I wanted to. I loved them but all they did was collect dust. They were gifts from family members, including my mom who is gone now. I miss them now. I guess one has to draw the line somewhere, but I wish I had room to store such things and rotate them in and out of display. A friend of mine has a huge basement and does that, she "redecorates" her house often, just re-arranging her collections. That's the plus about display shelves, you can rotate various items on them, including picture art. But again, I'm not a minimalist. Depends on the vibe you are going for. I love the idea of black and white art. I have that in my family room, black and white Japanese wood block prints with black lacquer frames.

I liked the look so much I bought a calendar with art pages of Japanese wood block prints and watercolors and then some cheap plain black frames at Michaels to put them in to create a montage. Really nice looking and quite inexpensive.