Everyone who replied against standardization should consider the fact that many of my most successful photo artist clients compose in the viewfinder and I dare not crop their artistic efforts, and print full frame for them. Some use the standard mats that I supply, others buy the stock sizes, single, double or whatever, as sold by suppliers such as Redimat. Recently I printed for 3 photographers who entered their work in our local Amador County Fair. Out of the 12 prints that I made for them, 10 placed first or second in their various classes, and one print won a best of show. All were 'standard' sizes. If someone buys a particular photo it's not because the size is unique or doesn't fit the norm, it's because the image is unique, outstanding, or because they love something about the artist's vision. Most working photographers don't want to get caught up in the minutea of matting, framing, and other chores that take away from their time doing what they do best...taking photographs. Also, a lot of the galleries here in California are also frame shops. They like their exhibitors to leave the fancy framing to them. After the print is sold, the customer sometimes will choose a custom frame or mat to suit their taste. The bottom line is...do whatever your market dictates. Study the photographers who are really selling. I don't mean a print here or there, I mean photographers who make a living from their photography. Chances are that they are most concerned about the quality of the print and how it conveys their artistic effort, and most likely use a simple frame and mat that does not distract from the image.