mbecher

This plugin will extract the large version of an image attached 
to a post and put it in front of the content in the RSS feed. 
This might be useful if you have an image (and only a single one) 
attached to a custom field and it won’t display in the feed otherwise.

RSS Custom Fields Images

Puts large sized image attached to posts in front of content in rss feeds. Useful for images in custom fields.

marapper

Manage custom fields using the insert shortcodes [custom name=”field-name” value=”field-value“] or HTML conditional comments <!–custom name=”field-name” value=”field-value“–> in text of post. It’s a hook for desktop blog clients, which don’t support customfields natively.
Простой хак Вордпресса, позволяющий управлять произвольными полями из любого внешнего клиента или при отправке через почту с помощью шорткодов [custom name=”имя-произвольного-поля” value=”значение“] или условных комментариев <!–custom name=”имя-произвольного-поля” value=”значение“–> прямо в тексте поста.

Custom Shortcodes

Manage custom fields using the insert shortcodes or HTML comment in text of post.

RSS Custom Fields Images vs Custom Shortcodes