Overlay images not available for displaying
From semantic-mediawiki.org
Fragment of a discussion from Help talk:Gallery format
I know this is old, but I just ran across this problem myself. On Windows servers, the href uses "%3A" instead of ":". Changing
var title = image.attr( 'href' ).split( encodedNsText + ':' ),
to
var title = image.attr( 'href' ).split( encodedNsText + '%3A' ),
on line 96 of ext.srf.gallery.overlay.js worked for me.