Welcome to therichpost.com. In this post, I will tell you, Get Featured Image URL WordPress.  Like I always say WordPress is the best cms. 

Here is the working code:

$thumb_id = get_post_thumbnail_id();
$thumb_url_array = wp_get_attachment_image_src($thumb_id, 'thumbnail-size', true);
$thumb_url = $thumb_url_array[0];

or

<?php if (has_post_thumbnail( $post->ID ) ): ?>
  <?php $image = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'single-post-thumbnail' ); ?>
  <div id="custom-bg" style="background-image: url('<?php echo $image[0]; ?>')">

  </div>
<?php endif; ?>

 There are so many tricks in wordpress and i will let you know all. Please do comment if you any query   related     to this post. Thank you. Therichpost.com