[mardup]

(...) The artist/extrafanart directory must already exist and there must be at least one image in the extrafanart directory. If both these things are not true, the images will be downloaded to the default cache directory. (...)

Thanks for your answer

It's a shame.

Many of my artists have no extrafanart (CDart MAnager plugin does not find any pictures) while this script (Artist Slideshow) displays many images for these artists.
I thought that progressively, I could fill my empty extrafanart folders.

Perhaps in a future release