The [[https://www.mediawiki.org/wiki/Manual:$wgForeignFileRepos|$wgForeignFileRepos]] configuration setting for {de,es,fi}.shoutwiki.com had the wrong (old) value for the directory key (essentially due to T41: Cleanup legacy image pathing), which tells MW where the physical files are stored at. This is fixed now, but you may need to purge the page to see thumbnails again.