alt tags?

Hey all. I have some php here which is set up to display a photo in the header of my theme. However, there’s no alt attribute and I would like to add it. Anyone have any ideas how it could be accomplished? Here’s the code<?php if ( get_option('thrill_snapshot') <> "" ) { ?><style type="text/css">#header .spacer{background: url(<?php echo bloginfo('template_url'); ?>/thumb.php?src=<?php echo stripslashes(htmlspecialchars(get_option('thrill_snapshot'))); ?>&h=137&w=137&zc=1&q=95) no-repeat 0 0 !important; margin:-28px 0 0 !important; padding:28px 0 0 6px !important;}</style><?php } ?>

thanks!