<?php if ( !isset($_GET['background']) ) { ?>
#footer {
    background-image: url(/media/images/spring-footer.png);
    background-repeat: no-repeat;
    background-position: top right;
    background-color: <?php print $light_grey ?>;
}

#footer_text {
    background: none;
}

#header_top div {
    background-image: url(/media/images/spring-left.jpg);
}

#header_top {
    background-image: url(/media/images/spring-mid.jpg);
}

#header_top div div {
    background-image: url(/media/images/spring-header.png);
}
<?php } ?>