I saw an HGTV show today where the beach house homeowner had made a wood ceiling out of ripped 6"-8" wide lengths off of thin plywood sheets. It was to mimic shiplap. Easy to hang. Looked great after painting!

Hi Lola! Depends in part on what specie/color of wood you used..... That looks like pine so you could probably use a clear oil like Messmer's UV+ and accomplish the same thing. It will darken the wood a little bit and bring out/maintain the natural colors. If you have any boards left over, to get a very specific color, have the person who will be applying it for you create a couple samples and test it on small swatches until you find the one you're looking for. Best of luck and let it know how it works out! https://www.soluslumber.com/shop/supplies/deck-seals-oils-finish/

I like the look now and wouldn't stain it, the problem with leaving it would be the way it coordinated with the wood floor. That said, I'd either leave it and change the floor color or make the contractor paint it. One question: Did the T&G sit in the house for two weeks with heat/AC running to acclimate it to the temp/humidity? If not, it's going to shrink or swell (probably shrink) when the house is closed up and heated/cooled. If you paint, you want to paint AFTER THAT. Otherwise, you'll have lines of unpainted pine showing through. The house will be near finished and the contractor will say "You really don't notice it from down here" and won't address the issue.

End matched is the term, though I don't know of any long boards available. You can use PVC biscuits and glue to join long boards. You can also mill your own with a router too.