Convert WordPress Default Captions Shortcode to HTML 5 Figure and Figcaption Tags
How to make WordPress use <figure> and <figcaption> instead of the default image caption shortcode output. Includes code for your functions.php file.
Custom Field Types & Featured Images in WordPress RSS Feed
How to add a custom thumbnail to your RSS Feed. This checks first for an explicitly set custom field value, then moves on to the WordPress post thumbnail, and finally displays a default image if none of the above are true.