hi
in fact, I think that 'cache stored images' tab never works.
a *simple* sized picture in a new content, as following, is not recached:
`[img]/cache/images/photos-du-mois/_mg-3167_500.jpg[/img]`.
hopefully, after changing some '_' in '-' in some news, I fixed my issue (cache images are generated), but I allways have to visit my news to generate cache images (whatever the size they have, custom or not).