Frederick Wilbur's book, Carving Architectural Detail in Wood provides most of what you mentioned. I don't think he covers shells, though those are easy enough to intuit.
It's interesting that you think carved details should add value to a piece of furniture. I agree, of course, but I think you'll find scant interest in carved pieces in the public, except for the 18th century furniture that employ shells, volutes etc. But, when I have a client who does appreciate it, its a real joy to produce the work. You might also look into doing some ecclesiastical carving, there's a market for that.
My offer stands, if you want to come up this way I'll show you what I can.
Regards,
John