Yes, there are stores that specialize in unfinished furniture in Knoxville,TN. You can find them at http://www.superpages.com/yellowpages/C-Unfinished+Furniture/S-TN/T-Knoxville/
Unfinished bookcases can be purchased at furniture stores that specialize in unfinished furniture, online retailers such as Wayfair or Amazon, or local woodworking shops that offer custom furniture options. You can also consider flea markets or thrift stores for secondhand unfinished bookcases.
There are a number of online stores that sell unfinished furniture. The Wayside Workshop, which is based out of Aurora, offers unfinished furniture. Woodcraft Furniture, in Beechmont, also sells unfinished furniture.
Headboards from any number of countries can be found at most of the finer stores, and possibly any furniture stores or stores that specialize in bedroom furniture.
You can usually find furniture at speciality stores that specialize in restaurant furniture. If your looking for quality, it can be somewhat of an investment.
There does not seem to be good furniture store in San Marino that sells unfinished furniture exclusively, but a store www.millstores.com does deliver to San Marino. The normal furniture stores might have some unfinished furniture as well, but you might not get the extensive variety you are looking for. A good idea would be to rather travel some distance to a full-fledged store (check the one closest to you on the website suggested).
The "furniture" category will have plenty of furniture stores, some of which may specialize in children's furniture.
Unfinished wood furniture items can be bought on internet sites such as eBay, or from the private blogs or webpages of skilled craftsmen. Etsy is an online store where many craftspeople work, and one could easily find such an item there.
You can purchase unfinished cabinets and furniture online at websites such as Mill Stores and Kitchen Cabinet Depot. You may also be able to locate a nearby wood store that sells unfinished cabinets as well using the Yellow Pages.
There are several local and national furniture companies that sell rustic patio furniture. In addition to stores there are also several websites online that specialize in selling rustic patio furniture.
You can get inexpensive office chairs from stores that specialize in office furniture sales, such as offic max, or even directly from generic stores such as target.
There are many options. One option is to visit patio stores such as Patioworld that specialize in patio furniture. Also, for a cheaper option, you can check your local Target or Wal-Mart or Costco.
There are so many options when searching for quality in regard to any furniture in your home. I would look into local furniture shops and stores that specialize in wooden furniture.