According to the SmiliesPlugin documentation:

   * The name of the topic containig _[sic]_ your Smilies. Default: TWiki.SmiliesPlugin 
   * #Set TOPIC = SmiliesPlugin 

The benefit of using a separate topic is to retain changes after applying a patch or upgrade. Unfortunately that feature doesn't work: if I set SMILIESPLUGIN_TOPIC to my own topic, the short cut and alt text from the new topic are recognized. But the image is "broken" unless it is attached to the original plugin topic.

Here's the fix (I don't have access to check it in, or time to learn how to run the test cases). The topic name is picked up from the preferences (if used) and parsed into $web and $topic. But then those variables aren't used to create $smiliesPubUrl:

    $topic =
      TWiki::Func::getPreferencesValue( 'SMILIESPLUGIN_TOPIC' ) 
          || "$installWeb.SmiliesPlugin";
 
    $web = $installWeb;
    if( $topic =~ /(.+)\.(.+)/ ) {
        $web = $1;
        $topic = $2;
    } 

[... elided ...]

    # MODIFICATION

    #$smiliesPubUrl =
    #  TWiki::Func::getUrlHost() . TWiki::Func::getPubUrlPath() .
    #      "/$installWeb/SmiliesPlugin";

    $smiliesPubUrl = TWiki::Func::getUrlHost() . TWiki::Func::getPubUrlPath() . "/$web/$topic"; 

P.S. I think I'm using the current version of the plugin. On the plugin topic itself, it says "Plugin Version 21 Nov 2007".
But on InstalledPlugins, it says (Dakar, $Rev: 16049 (11 Aug 2008) $)

-- SeanMorgan - 12 Nov 2008