I’d just play around with different arrangements.

For instance, this is one I like: a taller vase and candle on left, with lower items on right (I wouldn’t do the stack of books).

I usually prefer odd numbers, though … so three on one side, two on another. But it’s really subjective.

Are you wanting a more minimal look?

Another idea is the two candles on the left, with just the bowl on the right.

Are you open to getting new artwork? Ideally, the width should be close to the same as the fireplace opening. If not, I would lean the picture on the mantel, with the left side just inside the edge of the firebox. Overlap the two candleholders (use matching candles) to the left of the picture (somewhat overlapping each other). On the right side of the artwork, add a "spiller" plant in a long, low pottery pot.

“Another idea is the two candles on the left, with just the bowl on the right.”

I like that. Mantels always look best to me when simple.

As Sammie suggested, use the same color candles.

I like those ideas. I do have a pair of electric candles. When I unwrapped the plastic the candle pretty much exploded. Lol. We live 85 miles from the store. Will
exchanged it when we we go back next week.

Better? I do like it!

Maybe a spiller plant in the bowl?

I would get another blue candle for the shorter hurricane. A plant would be nice for the bowl…a real plant. At some point you might also consider non-glare glass for the art.

How about candles in the fireplace? Battery operated ones work well. I found some battery twinkle lights at Dollar Tree that I really enjoy.

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Maybe a nice fern?

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To lighten for summer you might try a mirror unless it will reflect the kitchen or other not so pretty view. Your mantel seems very narrow, so you may not be able to layer much on it. Stringing things out like soldiers isn't a good look, IMO. Rather stay simple than do that.

So many great ideas! I do like the plant in front of the fire box. And I want to keep it minimal, so maybe no plant? My hubs and I designed and built the mantel and fireplace wall. Behind the wall is a black lava rock wall built into the fireplace blocks. So we couldn’t rip it out so we coveted it! We can easily add another layer of wood shelf that is deeper to have more room.
Thanks!