Andrew Gray, 11/10/2011 20:11:
It may be that more controversial images provoke more meta-discussion, with more links to them as a result (from talkpages, deletion discussions, etc) and so are more likely to appear "popular" to the search system, but that's just a guess.
Hm, Lucene Streisand effect.
Béria Lima, 11/10/2011 20:31:
I guess that has something to do with the name of the images. The sexual image has the name of File:Sexuality *pearl necklace* small.png
http://commons.wikimedia.org/wiki/File:Sexuality_pearl_necklace_small.png
so, would be obvious to be one of the first results if you are looking for *pearl necklace*.
Looks like there are 248 exact file matches. https://commons.wikimedia.org/w/index.php?title=Special%3ASearch&search=%22pearl+necklace%22&fulltext=Search&ns6=1&profile=advanced I see that the first image doesn't use information template, perhaps descriptions within templates are treated differently? Could be a wrong assumption based on how infoboxes work on Wikipedia. (Just more imaginative speculations...)
Nemo