HTML

<p><a href="image/image-1.jpg" rel="lightbox" name="ここがタイトルになります"><img src="image/thumb-1.jpg" alt="" width="100" height="40" /></a></p>

lightbox.js

218行目の
this.imageArray.push([imageLink.href, imageLink.title]);
を
this.imageArray.push([imageLink.href, imageLink.name]);