Create the field and then create a new template called link_sponsored.html (just save link.html as link_sponsored.html). Then you can modify this new template to get the sponsored listing looking how you want.

sub {
# Displays the sponsored links on every page.
my ($output,$sth,$link);
my $search_db = $DB->table('Links');
$search_db->select_options ("ORDER BY rand()");
$sth = $search_db->select ( { sponsors => 'Yes', isValidated => 'Yes'});
while ($link = $sth->fetchrow_hashref) {
$output .= Links::SiteHTML::display ('link_sponsored', $link);
}
return $output;
}