Change Search Button to Image

How do I change the search button to an image instead?

<form method=”get” id=”searchform” action=”<?php echo $_SERVER[‘PHP_SELF’]; ?>”>
<div><input type=”text” value=”<?php echo wp_specialchars($s, 1); ?>” name=”s” id=”s” /><input type=”submit” id=”searchsubmit” value=”Go” />
</div>
</form>

I think this is all the css I found for above.

#searchform {
margin: 10px auto;
padding: 5px 3px;
/* text-align: center; */
}

#leftsidebar #searchform #s, #rightsidebar #searchform #s {
width: 115px;
padding: 2px;
}

#leftsidebar #searchsubmit, #rightsidebar #searchsubmit {
padding: 1px;
}