An unexpected aspect of sharing photos on Flickr or other social media and offering them for sale as stock images is realizing that some of the most popular photos (in terms of the number of views, sales, etc.) are not my personal favourites. I believe that this is a feature of broadcasting to a very large audience, as opposite to “narrow casting” to a small community of personal friends, who generally have similar tastes and interests to my own.
Sometimes, however, I have a sense that an image has a potential to become popular even before I post it. It usually has to do with the subject, as in the photo of ukai (fishing with cormorants) that I took in Inuyama, or the unique viewpoint, as in the shot of Niagara falls taken from a helicopter.
Otherwise, I find that even if the image has some of the components that can potentially make it interesting, such as motion and emotion, if the audience cannot relate to or immediately recognize the subject (e.g. the Eiffel tower or the Great Wall of China), their engagement in terms of views, shares over social media, etc. will be limited.