Index: wp-content/plugins/wp-rss-images/wp-rss-images.php
===================================================================
--- wp-content/plugins/wp-rss-images/wp-rss-images.php	(revision 538837)
+++ wp-content/plugins/wp-rss-images/wp-rss-images.php	(working copy)
@@ -91,10 +91,23 @@
 
 }
 
+/**
+ * Returns a URL to an image in the user uploads directory on this server.
+ *
+ * Developers can hook the wp_rss_image_alternative filter to provide their 
+ * own image URL on this server, or hook the wp_rss_image_size filter to 
+ * provide a specific size for the featured_image.
+ *
+ * @param string $size Defaults to medium, a WordPress image size added with add_image_size
+ * @return string The URL to an image on this server
+ */
 function wp_rss_img_url($size = 'medium') {	
 	global $post;
-	if( function_exists ('has_post_thumbnail') && has_post_thumbnail($post->ID)) {
+	if ( $img_url = apply_filters( 'wp_rss_image_alternative', false, $post->ID ) ) {
+		return $img_url;
+	} else if( function_exists ('has_post_thumbnail') && has_post_thumbnail($post->ID)) {
 	    $thumbnail_id = get_post_thumbnail_id( $post->ID );
+		$size = apply_filters( 'wp_rss_image_size', 'medium', $post->ID );
 		if(!empty($thumbnail_id))
 		$img = wp_get_attachment_image_src( $thumbnail_id, $size );	
 	} else {