Unique Carvings
To be unique there should only be one kind of carving in existance. I suspect this is hard even for high end carvings. An artist who finds a motiff and materials which sell well is going to continue to make works in a similiar manner. There will only be so many variations which are possible. So the carvings will be unique in exact details, but also need to provide the "look" for which the carver is known.
Below are listed Ebay sales for "Carvings". Clicking on any of the links will take you directly to that auction. I am sure many are not unique, but some certainly are. Carbing is done is so many materials that a collector can pick and choose the kind of items they like.
At the simple end of the market unique carvings can be made by anyone with a few sharp knives or a dremel tool from whatever materials they have around. In particular, I have seen wood carvers do well with scrap wood they pick up themselves or waste from a cabinet shop or other wood related business. In fact wood for carving is a good business on Ebay. That said, and given the prices paid for carved folk art, I think unique carvings might be a make and sell item that could be profitable for a variety of folks.