The following article would show how to add lightbox feature to an Omeka theme.
Download lightbox and place the lightbox directory inside /themes/theme-name/common/ directory.
now open the /themes/theme-name/common/header.php in an editor and add the following code before

<!– Start Lightbox includes –>
<link rel="stylesheet" media="screen" href="<?php echo WEB_ROOT;?>/themes/theme-name/common/lightbox/css/lightbox.css" />
<script type="text/javascript" src="<?php echo WEB_ROOT;?>/themes/theme-name/common/lightbox/js/prototype.js"></script>
<script type="text/javascript" src="<?php echo WEB_ROOT;?>/themes/theme-name/common/lightbox/js/scriptaculous.js?load=effects,builder"></script>
<script type="text/javascript" src="<?php echo WEB_ROOT;?>/themes/theme-name/common/lightbox/js/lightbox.js"></script>
<!– End Lightbox includes –>

Now the ground work is done and it’s time to add the lightbox functionality to the item show page. Open the Now Show.php page located in /themes/theme-name/items/ and replace …