You'd be surprised that just going to a craft store and asking an associate would probably help you out a lot. They typically get good ideas from their customers (doing the same thing as yourself) and are usually fine with sharing.
Some ideas for Thanksgiving decorations include candles and fall flowers. You can get ideas at http://www.marthastewart.com/photogallery/thanksgiving-tables-for-kids and http://www.countryliving.com/cooking/entertaining/thanksgiving-table-settings-1108
I would talk with someone in the retail outlet that you are interested in purchasing the decorations from. They often have traning in this area, and should be able to assist you.
The cheapest Thanksgiving table center pieces are always the homemade ones. That said, if you prefer to purchase something, a plethora of options can be found at Kitchen Daily: http://www.kitchendaily.com/2010/10/25/thanksgiving-table-decorating-ideas/
Terrysvillage.com is a great source for Thanksgiving decorations. As always Walmart and Target also have nice selections. For a nice table piece you should look at bhg.com which has many ideas on something you can put together yourself.
If you are looking for Thanksgiving decorations to decorate your table, there are many options. Discount stores such as Walmart and Target carry a wide variety of holiday decorations. Department stores such as Sears and Kohls also carry this type of decoration.
Ideas for Thanksgiving centerpieces can be found at several retailers especially craft store. Different ideas are a floral centerpiece using warm fall tones, a cornucopia arrangement, or just an old fashioned ceramic turkey figurine.
I always like the turkeys made from tracing there hands. Have the kids trace their hands on paper and then color them in as a Turkey.
There are quite a few ideas for unusual wedding table decorations. Lanterns are a rather unique idea for table decorations - and particularly effective if the meal is taking place outside and in the evening. Seashells and coral are also quite an unusual wedding table decoration.
You can decorate with turkeys, gourdes/squash, dried fall leaves. Fall colors for table linens, and candle center pieces. Pilgrims and Indian displays are always fun too.
Online. You could also visit any local retail store around the holiday. Almost all retail stores have thanksgiving decorations out months ahead of time. They don't have what your looking for or anything that suits your taste. Looking online is always a way to get something unique and for a good bargin.
Could you be more specific? Could you describe the table? On MY table, the turkey is the centerpiece.
You can go to almost any wide retail outlet to make this purchase. Places such as target and kmart also sell table decorations that you would be able to use for your party.