add_action( 'wp_head', 'sk_customizer_css' );
/**
 * Writes the Home Top background image out to the 'head' element of the document
 * by reading the value from the theme mod value in the options table.
 */
function sk_customizer_css() {
?>
	 <style type="text/css">
		<?php
			$sk_home_top_background_image_url = wp_get_attachment_url( get_theme_mod( 'sk_home_top_background_image' ) );
			if ( 0 < count( strlen( ( $sk_home_top_background_image_url ) ) ) ) { ?>
				.home-top {
					background-image: url( <?php echo $sk_home_top_background_image_url; ?> );
				}
			<?php } // end if ?>
	 </style>
<?php
}