I've been selling B&W photos at the local annual arts & crafts fair for 30 years. Most prints have been about 10x14 on RC paper with a recent shift to digital printing on an Epson 3800. Buyers in this rural area don't seem to be concerned with fiber, RC, or digital printing. Matted prints sell about as well as framed ones. Frames are basic aluminum frames in black and silver. It's easy to remove the frames if a buyer desires, or frame a matted print on the spot. By standardizing mostly on one size image and mat, the mats and frames can be interchanged and can be purchased in quantity for discounts. 5.5x8 images in inexpensive 8.5x11 document frames provide a quite affordable alternate to the larger prints. Framed prints have labels on the back giving my address and a little biographical information.
Display panels fabricated from pegboard 30 years ago have earned their keep. They hold up to 32 16x20 frames. Unframed photos are in a bin. Trifold brochures and business cards produced on a laser printer give potential buyers something to think about and remember the photos by. A schedule of events for the fair is posted on the panels for the convenience of passers by, and in hopes that they will linger and look at the photos. Sometimes, like Tony, I set up an older Speed Graphic camera for those who have no experience with larger equipment. I also offer a guarantee and will buy back or exchange any photo previously purchased. So far nobody has wanted to do this. Customer service is important for repeat customers.