There are photo experts who claim that the only ratio you should be working in is full frame; at the ratio of your camera. The even more extreme view is that you need to do this always in landscape mode, as we have two eyes, and see is some type of landscape mode rectangle. While I can appreciate the work that proponents of these views produce, my own view is that the strongest crop for a given image is the right crop; and that consistency and convenience for those matting and framing the images is not a top concern.
There is another reason for producing a wide range of image formats, especially for stock photos: graphic designers are always looking for the right image to fill a header, a banner, or a narrow column at the side of a screen or page. If you offer dynamic images in a wide range of shapes, you are far more likely to sell images for graphic and web design.
To illustrate this concept, I searched my library for the most extreme of forms: the vertical panorama, a form I use quite frequently. I then sorted through a number of these shots to find my “most vertical pano”… the image with the most extreme aspect ratio that continued to work well as an image, and to effectively tell its story. Its not surprising that a vertical city of New York provided my extreme vertical pano winner.
Here you can see that this image works based on a single sided streetscape, with low key features well grounded at the bottom, and high key features filling the higher sections of the image. It is an effective story-teller, and could certainly be printed as a fine art image, but its real strength would be in adding the needed vertical element to a web page or printed page.
C. David Tobie