Here is an example of how you can put a background image in the loadarea
it works best if the images are the same size, at least the other pictures should not be smaller than the background pic.
About the link, take a look a this from the doc
<a href="myimages/first.jpg" title="This is a picture of my dog!" rel="enlargeimage" rev="targetdiv:loadarea,link:http://cnn.com">Thumbnail</a>