Error creating thumbnail: convert: Unrecognized option (-thumbnail).
Fragment of a discussion from Project:Support desk
i am interested in knowing as well.
You don't have image magick installed, or more likely have another program thats not image magick installed with the name convert.
You need to either set manual:$wgUseImageMagick to false in LocalSettings.php, or install image magick, or fix where mediawiki is looking for image magick (manual:$wgImageMagickConvertCommand).
