Use a random picu collection image as background

random-picu-collection-image-as-background.php

/**
 * Use a random collection image as background.
 *
 * @param string $custom_styles CSS code; Make sure to add your code to the string and not overwrite it.
 */
function my_picu_delivery_random_collection_background( $custom_styles ) {
	$post = get_post();
	$delivery_option = get_post_meta( $post->ID, '_picu_collection_delivery_option', true );

	if ( $delivery_option == 'upload' AND ( 'delivery-draft' == $post->post_status OR 'delivered' == $post->post_status ) ) {
		$images = get_post_meta( $post->ID, '_picu_collection_delivery_ids', true );
	}
	elseif ( 'draft' == $post->post_status OR 'sent' == $post->post_status OR 'approved' == $post->post_status ) {
		$images = get_post_meta( $post->ID, '_picu_collection_gallery_ids', true );
	}
	
	if ( ! empty( $images ) ) {
		$image_ids = explode( ',', $images );
		shuffle( $image_ids );
		$image = wp_get_attachment_image_src( $image_ids[0], 'thumbnail' );
	}

	if ( ! empty( $image ) ) {
		$custom_styles .= 'body { background: url(' . $image[0] . ') fixed; background-size: cover; }';
	}

	return $custom_styles;
}

add_filter( 'picu_custom_styles', 'my_picu_delivery_random_collection_background' );