Chetan Satasiya

This plugin will Add Featured Image or Post Thumbnail to RSS Feed.

CS Add Featured Image to RSS Feed

Simply the best & most effective solution to the common issue of getting featured image on RSS Feed – full marks!

Excellent – simple and effective

This plugin will Add Featured Image or Post Thumbnail to RSS Feed.

tepelstreel

The RSS-language will change the tag of your feeds from the default (‘en’) to the language of your WP installation by default. In case you are e.g. using French as the WP language, but want to publish in Dutch, you can change the language in the settings section. Nothing specific will change in the feed but your blog will be found easier by people using the language, you are actually writing in. Also it helps search engines to list your site correcly, if you provide the feed as a sitemap.
The plugin was tested up to WP 3.4 and should work with versions down to 2.7 but was never tested with those.

Native RSS

Changes the  tag of your feeds to the language you are publishing in.

CS Add Featured Image to RSS Feed vs Native RSS