One of my aims when I opened my Etsy shop selling vintage graphics was to have as wide a variety of images available as possible. It took me a while before I realised this was tapping into something called the 'long tail'. The graph shows how this works. The area in yellow is the same as the area in green, but represents a large number of distinct items sold in relatively small quantities, rather than the small number of items sold in large quantities represented by the green area, which is where the best sellers like the Dan Brown books or '50 Shades' series are to be found.
By aiming for wide variety, I am targeting this long tail. At first this was an accident, now it is a deliberate tactic. Note that this is not the same as catering for a 'niche' market. As a strategy, niche marketing is aimed at being a big fish in a small pond, concentrating all your efforts on a small but specific and well defined segment of the population. Catering to the long tail is the opposite. Because I print to order and therefore don't have to either anticipate what will sell or keep large stocks, I can spread my efforts very widely. As a comment on the Longtail blog linked at the end of this article put it "The market is a mile wide and an inch deep".
I'm not alone in this of course, this is the Amazon model where over time products with a low sales volume collectively make up a market share that rivals or exceeds the relatively few current bestsellers and blockbusters, provided that distribution channel is large enough. This is why I wouldn't attempt this approach on an independent web site. Etsy as a brand already brings huge numbers of people to their site and I can tap into their searches to make my sales.
This possibly also explains why original art doesn't sell so well on Etsy or similar sites. The market for 'things to hang on the wall' is huge. That part of it looking for original works of art is much smaller. Out of that smaller market the proportion who will like your style and subject will be even smaller even if they find you. In addition, since the search process relies on using words to find images, the search terms for original art are very much harder to pin down, especially for abstract art. There are visual search tools but they do not have the reach of Google text searches. In my case it is even more difficult because Etsy's failure to properly differentiate between reproductions and originals or even between a downloadable file and the physical image once printed, makes the search results whether on site or via Google, hopelessly contaminated.
Based in part on: https://en.wikipedia.org/wiki/Long_tail
I didn't find it until I'd finished writing, but see also this site: