Background images are grate for placing other elements in front of the wallpaper, but normally not clickable... You can create a image map and make areas clickable, some use a transparent image over the background wallpaper and make it clickable.... kind of defeats the use of wallpaper!
But if all you want is to make the entire background click-able without moving it to the foreground, then all you need do is create a normal text link in the space where your background image would of been.... be sure to use the ID tag in the link... (id="nolinkImage")
Code:
<a href="http://www.mysite.com" title="my web site name or SEO" id="nolinkImage">my web site name or SEO title</a>
remove the background image in the stylesheet you already have for that space and add the ID tag for the link. We will create a box for the link.... you need this box to be the same size of ether the space or the image... say my image is 850 wide and 98 high, then so should be my box. next, we don't want to see the words, so we move them off stage...
Code:
#nolinkImage {
background-image:url(mybackground.jpg);
background-repeat: no-repeat;
display:block;
height:98px;
width:850px;
text-indent:-9999px;
}
The link goes in your template includes\templates\MY_TEMPLATE\common\tpl_header.php
and the style goes in your includes\templates\MY_TEMPLATE\css\stylesheet.css