What's with the free images?
Herkko A. Hietanen, Kumaripaba Athukorala, Antti Salovaara · 2011
Our survey of the Flickr photo site's Creative Commons attribution licensed images reveals that there is a wide variety of high quality of relevant stock images available. However, searching the images can be demanding since the image metadata is inconsistent. The main problem of finding open images is that the search tools are mostly based on user generated tags. The search results would benefit from human sorting and simple machine vision analysis. These steps might be able to close the gap between commercial stock photo and open image collections.