Issues loading files from within css files
For static assets I usually use something like this:

{% if craft.debugMode %}
    {% set assetsUrl = siteUrl %}
{% else %}
    {% set assetsUrl = "assets.mysite.com" %}
{% endif %}


And then I can set assets URL's the same way as navigation URLs. ie.

{% includeJsFile assetsUrl ~ "js/init.js" %}

{% includecss %}
body.landing #page-wrapper {
    background-image: url(" {{ assetsUrl }}img/pic01.jpg  }}");

}
{% endincludecss %}