There's not a way to add a link in CSS, but as a workaround, you can add a link in a text widget and then comandeer it with CSS to overlay it over the top of your header photo in Chaotic Soul.
First, add a text widget with the following content:
<a href="http://fairegarden.wordpress.com/"> </a>
Next, find out the id used for that specific header image. You can do that by looking at the page source after you add your text widget. It will be something like "#text-2". Then add this CSS:
#text-2 .textwidget a {
display: block;
width: 995px;
height: 151px;
position: absolute;
top: -183px;
left: 0;
z-index: 9999;
text-indent: -9999px;
}
Replace "text-2" with the ID from the text widget you added. If you have any trouble finding it, post back here after the text widget is added.