This works with the correct selectors (also in SMF 2,1 with our Portal system)   
 
 /* add Favicon to links with the class "bbc_link", but not in signatures! */
 $(':not(.signature)>.bbc_link').each(function() {
 var url = $(this).attr('href'),
 domain = url.match(/:\/\/(.[^/]+)/)[1],
 schema = url.match(/^(http[s]*):\/\//)[1];
 $(this).css({
 'background-image':'url(//www.google.com/s2/favicons?domain=' + schema + '://' + domain + ')',
 'background-repeat':'no-repeat',
 'padding-left':'20px',
 'background-position':'0'
 });
 });