I've enabled external images with the above statement in my LocalSettings.php, and try many syntax (from help text googled from web and mediawiki documentation). It appears nothing I've done has enabled external images or link to them. Only the working link to an image is displayed on my wiki page. I'm aware of notes that image links which do not explicitly look (to mediawiki's parser) like an image will be treated as a link.
Is there any step missing from the magic incantations needed to get external images? Thanks for any help.