Some kind of greenery on table and also in room. Perhaps change put pics to something with more pops of colour.

Do the books need to stay? I’d look at adding a side table

Would you consider adding wallpaper instead of art?

Doesn’t make sense to have all those books in the dining room, they don’t look good and you don’t read in the dining room. Plus the child will pull them outPaint the ceiling, put a buffet in place of the bookcases with something nice on it.

Agreed, ceiling definitely needs to be painted

I don't think books are necessarily wrong in a dining room. I've seen some combos that work. But they overwelm your glass table. You need a heftier table with a wood or stone top. Or pair the glass table with a simple buffet, maybe one painted a bright color. I would also consider a floor cloth. VMAT has some great contemporary-patterned ones that would pair well with your table and chairs. I used this one in my own MCM kitchen, underneath an Eames table: vinyl mat. A vinyl mat over our wood floor has been a godsend for making kid messes and spills less stressful.

Paint. I’m not a fan under dining tables. New chairs, lighting. Move at least some of the books and add interesting personal articles on the shelves, maybe a pretty bowl or basket.

^ i like the books but would add a few dining related pieces (maybe a few pitchers etc) - I agree the glass table feels anemic but I think a rug could help

Paint the walls and ceiling. Get a rug for under the table. I love seeing all books on the shelves. You are clearly a family that reads and needs a room for books. It is a lovely vibe.

@BeverlyFLADeziner 's color suggestion really makes the bookcase and light fixture stand out in a nice way. And, it looks fine with nothing hung between the windows. The second and third pictures are a vote for a dark rug rather than one that is lighter.

One of the rugs I posted is machine washable.

IMO bookshelves filled with books in a room where tyou do not read is odd. If you put a nice buffet ther then no problem with art on thta wall. If the books have to stay can that shelving be moved to a different wall or maybe just lower bookshelving. No rug in a DR with kids ever IMO washable or not I think the room could handle a bigger table but the doors limit space do you have to use those doors or can they be stored away and a bigger table used?

Can't see the rest of the room, but could you fit taller bookcases on either side of the doors, so the first thing you see when you look into this room isn't the clutter of books? You could then do a larger/taller piece of art between the windows.