alaingg

Simple plugin that allows to include the images into your wordpress rss, rss2. 
The plugin use the post/page thumbnail or the firt attached image to the post/page gallery. viste the <a href="http://web-argument.com/2008/11/09/wp-rss-images-wordpress-plugin/" rel="nofollow ugc">plugin page</a> for details.

WP RSS Images

Kishor Kumar

This plugin modifies RSS feeds and ATOM feeds as you want. 
in plugins “feedfile” directory all the files are listed
Just now it’s show your feed image (post image), if you want you modify you can easily modify.
<h4>How to use</h4>
Putting the following templates into the current theme folder, then you can use the customized feed templates instead of the default ones.
<ul>
<li>feed-atom.php – Atom Feed Template for displaying Atom Posts feed.</li>
<li>feed-atom-comments.php – Atom Feed Template for displaying Atom Comments feed.</li>
<li>feed-rdf.php – RSS 1 RDF Feed Template for displaying RSS 1 Posts feed.</li>
<li>feed-rss.php – RSS 0.92 Feed Template for displaying RSS 0.92 Posts feed.</li>
<li>feed-rss2.php – RSS2 Feed Template for displaying RSS2 Posts feed.</li>
<li>feed-rss2-comments.php – RSS2 Feed Template for displaying RSS2 Comments feed.</li>
</ul>
Note: 
When these feed templates are not in the current theme folder, WordPress’s default feed templates will be used.

feed-modify-on-your-choice

This plugin modifies RSS feeds and ATOM feeds as you want.

WP RSS Images vs feed-modify-on-your-choice