You can simply add custom content to the story at any place by using the New page → Empty page function. Either edit the page content by double clicking the icon using the built-in code editor or just add Title and Comment the usual way. jAlbum 20's new Details view mode is designed specifically for this skins needs; facilitates editing long comments.
<br> for a new line, or create paragraphs by using
<p> ... </p> tags. Naturally, any HTML code is allowed here.
Below is a thumbnails section. You can control which images treated as thumbnails by the Settings / Story / Design / Images / Thumbnail threshold setting or by manually setting the type in Edit mode → Image data → Treat image as box.