I think the shelves look nice as is. What is the size of the opening above the fireplace? Are you looking for tropical art?

I never choose art for anyone, go shopping , take a drawing of the space above the FP with measurements and find somethiing you love . I certinly do not think it should be tropical because you live on the water in FLA. Art.com has tons of pieces even available in different sizes .. The shelves are fine as is no need for anymore stuff there

The built-in shelves look nice. Check out the websites Art.com and Etsy.com for some artwork to consider. Here's an example from Art.com You'll want to find something that brings you joy to see every day.

Every shelf feels much of the same vs below and look to create a link with the art you choose and also the room.

I’d also fill in the arch.

Art is what you love, not where you live. Think about the colors you like-right now the living area has no color.

Art is personal so you should carry the measurement of hat space with as you shop local art galleries for the right piece. Buy what you like not something to "match" your decor. I would eliminate everything on the shelves and get 1 larger piece for each shelf.

Find art that you love and then light it up.

I also wonder if you only had something like a linear basket on the two lower shelves on the right if it wouldn’t balance the heaviness of the tv on the other side. Just a thought.

Florida ... season is coming and most towns/cities have art/craft shows every month that are worth visiting. You can buy original art right from the artist.

I have always been told that you should decorate shelves in a zig-zag . So the vases should be on opposite sides, books of varying stacks, etc.

That central niche would be a great place for a large and vertically oriented piece of art.