I made enough arches for the kitchen and the conservatory, as they have the same cathedral ceilings. I've changed my mind several times about wallpaper for this room. I chose a Les Chinoiseries paper that has muted florals.
First up was mimicking the adjustments to where the walls meet the ceilings - building up the outer edge just a bit and attaching the inner roof/ceiling, filling the gaps. It meant removing wood strips along where the ceiling meets the walls. These were 1/2" square strips of the room's length and were intended to support cross-ceiling beams. I had forgotten the fun of prying out nails, sanding, filling, and priming. I had to re-route some tapewire in the process. The lighting would be similar to the kitchen so it would need a path up to the very top, and then out to the roof.
The wallpaper went up like a dream, as has been my recent experience with Les Chinoiseries paper. Once the paper was up, I attached the arches, and the lighting. The Ray Storey lights I used in the kitchen are no longer available as he has retired. I got similar ones from Lighting Bug, though they are smaller. I also have 3 LED can lights in the peak of the ceiling to add more light. Those are really hidden but provide more ambiance to the room.
The Sue Cook corbels - they got held up for months. Just as Sue shipped them, the Royal Mail had a cyber security attach and everything leaving the country got halted. They have now finally arrived and are now on my to do list.