Its been about 15 years since I did any tin ceiling. I used a source out of Quebec at the time that also sold stair railings, etc.
There are some 2x2 panels that are one big panel, then their are some that have 4- 1' squares on them, and some with a 6" square pattern.
You'll have to see how, in the case of the "one big panel" - how many you can put across the room without cutting. Same goes for the other patterns, but, you can cut them down the seam which obviously gives you a lot more room to play, especially with the 6" pattern.
I always used a pebbled "filler" sheet around the perimeter along with a tin cornice moulding.
I know there is a company in the States - "Norman" something - they used to have all the old dies and could make some pretty amazing stuff - it was just very expensive.
Finally, I think someone mentioned nails - make sure to get the ones made for tin ceilings.
