17th century cambered ceilings

I am currently looking at some cambered ceilings in the first floor of an early 17th century manor house in Lancashire. This type of ceiling was used throughout the main rooms (4) and incorporates an axial beam which is morticed into a cambered tie beam, with joists of relatively thin scantling set on an angle. There are no signs that the tie beam was decorated so the ceiling soffit was always plastered out for the entire ceiling. The ceilings are now plain plaster modern finish but I would be interested to know of any other examples, to see how they were originally finished - a flat plaster finish or more decorative?