Most rug dealers and rug websites get much better profit margins, as well as much tighter quality control, by importing new and used rugs through their own regional expert buyers, so there are very few who will buy used rugs on the open market here in North America. However, consumers who are interested in used rugs aren't concerned with margins, inventory costs, reselling efforts and markup amount, so your best bet is to find an interested, individual buyer.

If you think your rug has exceptional value for the price that you're asking, an appraisal and pictures might be mailed to some rug importers or dealers - but know that you're competing with their higher overseas margins. So, in selling to a dealer, it most often yields an unattractive price for either the buyer or the seller in these cases. If your rug truly is a good value for a buyer, you can likely get a higher price from an individual, than by going through a dealer.

I'd say the best selling method for a collectible rug is to have the rug professionally appraised and then to use eBay to try to sell it. If your initial appraised price seems at all low, get a second appraisal. It can be very important, in getting your asking price, to include any documented appraisal that was done. Set your Reserve price, in the eBay selling auction, at no less than the higher of your desired asking price or its professionally appraised value, so that you don't get short changed on its selling price. And set the auction for the maximum time available - do a 10 day auction, not something shorter, like the 3 day auction. You need to allow enough time to reach as many interested buyers as possible. The large volume of buyers at eBay (consisting of both consumers and smaller rug dealers) normally offers you the best chance to show your rug to many interested buyers - and competition among buyers results in higher final selling prices. Your Reserve should be sufficient so that you're happy to sell your rug at that Reserve price or higher. So the only thing you have to lose is the time it takes to create your listing. There are many rugs listed at eBay, typically several thousand. You can search those in your price range to see what elements others have listed - a very thorough listing is another key to maximizing your sales price.

Here are some relevant eBay links for you:
  Selling items using a Reserve price
  Oriental Rugs selling at eBay