I didn't set $wgUploadPath. Just
$wgUseInstantCommons = true; The
images URLs are actually transformed to remote URLs:
I work on my own local wiki, which address is
http://localhost/mediawiki/ and transcluding
{{mediawikiwiki::User:Peter17}} which contains
[[File:Exquisite-network.png]] produces: <a
href="http://www.mediawiki.org/wiki/File:Exquisite-network.png"
class="image"><img alt="Exquisite-network.png"
src="http://upload.wikimedia.org/wikipedia/commons/e/e1/Exquisite-netw…
width="128" height="128" /></a>, so, it actually points to
MediaWiki
image description page and Commons image.
I think he points that the will be wrong unless $wgUploadPath is a full
url (it is set as a full url for wmf wikis).