Added extra support example

.support/2023-09-16-random.php

@@ -0,0 +1,19 @@
+<?php
+/**
+ * Plugin Name: Default Featured Image - Random post image
+ * Plugin URI:  https://wordpress.org/support/topic/multiple-featured-images-6/
+ * Version:     1.0
+ */
+
+add_filter( 'dfi_thumbnail_id', 'dfi_random_image', 10, 2 );
+function dfi_random_image( $dfi_id, $post_id ) {
+	if ( get_post_type( $post_id ) !== 'post' ) {
+		return $dfi_id; // This is not a post, we only check posts.
+	}
+	$random_image_ids = array(
+		123, # Add your image id's in this array.
+		456,
+	);
+
+	return $random_image_ids[ array_rand( $random_image_ids ) ];
+}