Search box

I have placed a general search box with this code:
‘<form method=”get” id=”searchform” action=”<?php bloginfo(‘home’); ?>/”>
<div><input type=”text” size=”18″ value=”<?php echo wp_specialchars($s, 1); ?>” name=”s” id=”s” />
<input type=”submit” id=”searchsubmit” value=”Search” class=”btn” />
</div>
</form>’

But I would like the button to be a picture, like bootstraps, not a botton.
Can you please help with the code?

BTW, I find nowhere even the search widget…

Thank you,
Vera
P.S.I hope someone is there to help… Doesn’t seem this way…