I currently use 14x17 as my standard size for all 8x10 prints and smaller. However, 14x17 is NOT a standard frame size. You sometimes see 14x18 frames in stores, but even that is rare. Also, 14x18 does not look good with an 8x10 print.
I use 14x17 for several reason. First, it's a perfect size for mounting 8x10 both vertically and horizonally, and always looks balanced. It does not look overkill with the matting, but also does not cramp the print with it being too small.
The second reason I use 14x17 mat size is because it IS custom framing size! By selling prints in a odd framing size, it requires the buyer to have the print professionally framed, and not just slapped into a cheep Walmart frame. Most people do not know how to match a frame with a print, however...professional framers do, and I put my trust in custom frames to use a frame that harmonizes with the print. Also, custom frames are ALWAYS better quality then pre-made frames. I would prefer people not to use cheep frames with my prints.
Finally, I do not suggest using wooden frames for your photography. First off, several wood frames have impurities and chemicals in the wood and also in the paint/glazing used on the wood. These can be harmful to your print overtime and cause it to fade, yellow, ect. Also, the mat is usually held in place by staples against the mat, and its difficult to remove the print. By using metal frames, you can change prints out in a matter of minutes, and they also last longer and are more sturdy then wood, not to mention cheeper.
Regards,
Ryan McIntosh
www.RyanMcIntosh.net