#Commons as a source for "stock photography"

#Commons is not only #Wikipedia 's repository of illustrations, it is also a rich resource of freely licensed images that can be used for all kinds of other purposes. Commons does a great job for Wikipedia, but how do you measure its success for other purposes and how do you make it more successful.

I blog for instance and while I was in the Ardennes, I saw horses grazing above me, there is no picture that gives the same sense of nearby horses grazing above. In a previous blog I asked for pictures of the yak a running yak, a yak being milked, yaks in a caravan.

The question is, how do we compile the kind of pictures that are particularly illustrative, the kind of pictures that would make Commons a source for what you can also find in the collections of companies that sell pictures.

The difference with featured pictures is very much in the subject matter. There is only so much use for just another bug, bird or mammal. How do you illustrate back pain, love, madness, hard work, a person of a particular caste?
Thanks,
      GerardM