If it were me, I would not want to add another material to the mix so would likely repeat the board and batten look from the opposite wall

I think the board and batten, given a tongue and groove ceiling? Too much.

The board and batten is the side of a shed?To which you butted........what? A bar?

yes a counter that a pizza oven and smoker sit on. we used cement board

Perhaps use a vertical t&g on the below the countertop to related to the proposed ceiling.

I would never do a dark gray for a ceiling in almost any setting and outdoors it will look like a strom coming everyday . I love a blue ceiling in a porch maybe try that. As far as the rest IMO the B&Bis all wrong for an outdoor kitchen so no more for sure.You have a finish under the counter why not stain it like the rest of the wood you are working with but then of course to me white would be the logical choice to keep so many things have some kind of cohesion

We did the vertical slats thinking it would tie in the house. But I agree I don’t think I should do more. And this was the inspo for the dark ceiling.