Replace submit button with graphic

The search module for a CMS that I am presently using has following code. I will like to replace the generic submit button with a graphic (graphic.gif in root folder of site) of my own. Can someone please help me ammend this ? Thanks.
Code:

defined( '_VALID_MOS' ) or die( 'Restricted access' );

$button            = $params->get( 'button', '' );
$button_pos        = $params->get( 'button_pos', 'left' );
$button_text    = $params->get( 'button_text', _SEARCH_TITLE );
$width             = intval( $params->get( 'width', 20 ) );
$text             = $params->get( 'text', _SEARCH_BOX );
$set_Itemid        = intval( $params->get( 'set_itemid', 0 ) );

$output = '<input name="searchword" id="mod_search_searchword" maxlength="20" alt="search" class="inputbox'. $moduleclass_sfx .'" type="text" size="'. $width .'" value="'. $text .'"  onblur="if(this.value==\'\') this.value=\''. $text .'\';" onfocus="if(this.value==\''. $text .'\') this.value=\'\';" />';

if ( $button ) {
    $button = '<input type="submit" value="'. $button_text .'" class="button'. $moduleclass_sfx .'"/>';
}

switch ( $button_pos ) {
    case 'top':
        $button = $button .'<br/>';
        $output = $button . $output;
        break;

    case 'bottom':
        $button =  '<br/>'. $button;
        $output = $output . $button;
        break;

    case 'right':
        $output = $output . $button;
        break;

    case 'left':
    default:
        $output = $button . $output;
        break;
}

// set Itemid id for links
if ( $set_Itemid ) {
    // use param setting
    $_Itemid    = $set_Itemid;
    $link         = 'index.php?option=com_search&amp;Itemid='. $set_Itemid;
} else {
    $query = "SELECT id"
    . "\n FROM #__menu"
    . "\n WHERE link = 'index.php?option=com_search'"
    . "\n AND published = 1"
    ;
    $database->setQuery( $query );
    $rows = $database->loadObjectList();
    
    // try to auto detect search component Itemid
    if ( count( $rows ) ) {
        $_Itemid    = $rows[0]->id;
        $link         = 'index.php?option=com_search&amp;Itemid='. $_Itemid;
    } else {
    // Assign no Itemid
        $_Itemid     = '';
        $link         = 'index.php?option=com_search';    
    }
}
?>

<form action="<?php echo $link; ?>" method="get">
    <div class="search<?php echo $moduleclass_sfx; ?>">
        <?php echo $output; ?>
    </div>

    <input type="hidden" name="option" value="com_search" />
    <input type="hidden" name="Itemid" value="<?php echo $_Itemid; ?>" />    
</form> 

Code (markup):

 

maybe you should put the css file too here..

 

Maybe this is what u looking for?

<input type=image src="image.gif" name="submit">

 

looks like nasty php stuff.

As above is the simpliest

 

Replace the button definition on you 13th line with this:

$button = '<input type="image" src="graphic.gif" value="'. $button_text .'" class="button'. $moduleclass_sfx .'"/>';