Add tags to images for individual posts on Feedburner

I know how to add <media:content> tags to a regular RSS feed in WordPress, but I need to add them to my Feedburner feed. So is there a way to use some sort of custom tags on my images in WordPress so that Feedburner adds the <media:content> tags for the images in the RSS feed?

If you are curious, the reason is for a Mailchimp newsletter. To better understand what I am trying to do to my Feedburner feed, check this out:

http://blog.mailchimp.com/rss-to-email-enhancement-for-publishers/