You might be able to do this with something like this jQuery.
<@liaAddScript>
;(function($) {
var breadcrumbs = $('.BreadCrumb').find('>ul');
breadcrumbs.insertAfter('<li class="lia-breadcrumb-node crumb"><a id="custom_bc_link_1" class="lia-link-navigation crumb-community lia-breadcrumb-community lia-breadcrumb-forum" href="/my/url">Main Site Home</a></li><li class="lia-breadcrumb-node crumb"><a id="custom_bc_link_2" class="lia-link-navigation crumb-community lia-breadcrumb-community lia-breadcrumb-forum" href="/my/other/url">Secondary Page</a></li>');
})(LITHIUM.jQuery);
</@liaAddScript>
I am unable to test this right now.
Just upload your image under Studio > Community Style > Images. Check the radio button next to "icon_list_separator_breadcrumb.png" to replace that image with your new image.