Title and subtitle, and whether you want a restriction on the page or not, is defined in the JSON companion file.
Write your markdown here.
If you have images, just don't give them a JSON file, and they'll be served.

This is standard markdown.
XML:
<xml>
    <too>hot to handle</too>
</xml>JavaScript:
renderer.renderMarkdown = function (res, layout, apiResponse, body) {
    var metaInfo = { showTitle: false };
    var metaInfo64 = apiResponse.headers['x-metainfo'];
    if (metaInfo64)
        metaInfo = JSON.parse(new Buffer(metaInfo64, 'base64'));
    console.log(JSON.stringify(metaInfo));
    var title = null;
    if (metaInfo.title)
        title = metaInfo.title;
    var subTitle = null;
    if (metaInfo.subTitle)
        subTitle = marked(metaInfo.subTitle);
    var route = '/content';
    if (layout == "index")
        route = '/';
    marked.setOptions({
        highlight: function (code) {
            return highlightJs.highlightAuto(code).value;
        }
    });
    res.render(
        layout,
        {
            route: route,
            showTitle: metaInfo.showTitle,
            title: title,
            subTitle: subTitle,
            markdown: marked(body)
        });
}