Custom Thumbnail when none detected

This is explained on the plugins home page, the function below as it says will echo a thumbnail URL or the default image located at wp-content/plugins/video-thumbnails/default.jpg if a thumbnail cannot be found. So replace that image with your custom image. Use the code below, when a thumbnail is not found it will show your image.

<?php video_thumbnail(); ?> will echo a thumbnail URL or the default image located at wp-content/plugins/video-thumbnails/default.jpg if a thumbnail cannot be found. Here is an example: <img src="<?php video_thumbnail(); ?>" width="300" />