For a couple years, I ran a 70+ft charter boat from a respected yard with only a few sister ships, each of which had well crafted teak interiors. I was fortunate to visit a couple of the sisters, and what I saw, I think compares to what you see in your boat. The boat that I ran had been professionally decorated with a perfect combination of light, off-white panels of vinyl wall covering, highlighted with high-gloss varnished trim. And the difference between that and the sister ships was impressive.
Like Frank, I would not paint the lower panels, largely because that would be a virtually irreversible choice, and I don't think it is necessary. I would consider vinyl wall covering on the forward bulkhead, also on the panels flanking the companionway, and also on the panel at the forward face of the galley cabinetry and perhaps also vinyl on the panels above the main deck A simple beige runner carpet along most of the length of the sole will further lighten the space. All of the "solid teak" trim (as opposed to the teak veneer panels) should be varnished in high gloss.
Good quality vinyl wall covering is more visually interesting than paint, and should be more readily reversible or re-doable than paint.