Open a welcome message (image, inline, etc.) in a Shadowbox style

I am using the Shadowbox JS plugin in my self hosted wordpress at http://diariodebate.info in order to open my pictures, galleries, links and other stuff with this excellent plugin.

In shadowbox-js website, they mention this:

When using markup, each of these properties is automatically derived from the link element itself using the Shadowbox.buildObject method. But now that you know what’s really going on behind the scenes, you can just pass objects (or arrays of objects) that contain these properties to Shadowbox.open as in the following example:

<link rel="stylesheet" type="text/css" href="shadowbox.css">
<script type="text/javascript" src="shadowbox.js"></script>
<script type="text/javascript">
Shadowbox.init({
    // let's skip the automatic setup because we don't have any
    // properly configured link elements on the page
    skipSetup: true
});

window.onload = function() {

    // open a welcome message as soon as the window loads
    Shadowbox.open({
        content:    '<div id="welcome-msg">Welcome to my website!</div>',
        player:     "html",
        title:      "Welcome",
        height:     350,
        width:      350
    });

};
</script>

I wonder if is it there a way to do the same in this or any other plugin: to open an image, link, html, inline element, etc. by using this plugin and if somebody have succeeded doing it. Any ideas will be tested.

I haven’t found a solution yet, so I am using an index.html page previous to the index.php in order to show some content at the very beginning of the page.

Thanks in advance.

http://wordpress.org/extend/plugins/shadowbox-js/