WordPress customizer: add image upload (logo)

customizer.php

// Add theme customizer controls, settings, etc.
function kingdom_customize_register($wp_customize)
{
    /********************************************
	!  Image Upload
	*********************************************/
	$wp_customize->add_section('kingdom_image_upload', array(
		'title' => __( 'Images', 'kingdom' )
	));

	/* Logo */
	$wp_customize->add_setting('kingdom_logo_upload');
	$wp_customize->add_control( new WP_Customize_Image_Control(
		$wp_customize,
		'kingdom_logo_upload',
		array (
			'label' => __( 'Upload your logo', 'kingdom' ),
			'section' => 'kingdom_image_upload',
			'setting' => 'kingdom_logo_upload' 
		)
	));
}

/********************************************
! add controls / content to theme 
*********************************************/
function kingdom_display_contact_details_in_header()
{
	$html = '';
	$html .= '<address>';
		// Address
		$html .= '<p class="address">';
			$html .= get_theme_mod( 'kingdom_address_setting', 'Your Address' );
		$html .= '</p><!-- /.address -->';

		// Phone
		$html .= '<p class="phone">';
			$html .=  get_theme_mod( 'kingdom_phone_setting', 'Your phone number' );
		$html .= '</p><!-- /.phone -->';

		// Email
		$html .= '<p class="email">';
			$email = get_theme_mod( 'kingdom_email_setting', 'Your email address' );
			$html .= '<a href="' . $email . ' ">';
				$html .= $email;
			$html .= '</a>';
		$html .= '</p><!-- /.email -->';
	$html .= '</address>';

	echo $html;
}
add_action('kingdom_in_header', 'kingdom_display_contact_details_in_header');

functions.php

load_template( get_template_directory() . '/includes/customizer.php' );

header.php

/* action hook for any content placed inside the right hand header, including the widget area. */
do_action ( 'kingdom_in_header' );