I think the marble looks too small. We have a beach house and we decorated it to our taste. If you love black then do that one. The scale looks better. If you don’t like find one that says beach to you in a lager fee scale

I'd get a picture light (example) to illuminate the painting and not block it. Replacing the light over the dining table with a fixture that doesn't block light horizontally (like that Gregory chandelier?) would help. Maybe some wall sconces could be attached on either side of the large painting or on the wall with the skinny paintings.

-- amateur