To change favicon you need edit lib/perl5/site_perl/5.8.8/IkiWiki/Plugin/favicon.pm and change line:
$template->param(favicon => "favicon.ico");
at the end of file. And rebuild wiki:
ikiwiki -setup your_wiki_config
After reload page you'll see your new favicon.
That method allow configure Animated PNG even:
Typically sites that use animated pngs (ugh!) as favicons just call it
favicon.ico. It's not as if (most) web servers and browsers trust the filename extension to mean anything anyway. And using favicon.ico makes it more likely to work with old browsers that just always look for that. --Joey