Get image from wordpress widget and make it as background of particular section

I need to get a image from wordpress widget and want to set as a background image of a particular section. How can i do that?
previously i created widget areas by using php,

if (function_exists('register_sidebar')) {  
     register_sidebar(array(  
        'name' => 'Aim',  
        'id'   => 'aim',  
        'description'   => 'Widget area for aim',  
        'before_widget' => '<div id="%1$s" class="widget %2$s">',  
        'after_widget'  => '</div>',  
        'before_title'  => '<h2 class="test">',  
        'after_title'   => '</h2>'  
    ));  }

I can add image from IMAGE widget, but how can i make it as background of my particular section of my page from wordpress widget?