CoPress

Excellent question, Chris! Thanks for posting it. I think the ideal approach would be to build a small custom plugin that allows you to add either images in the post or images in a custom field as enclosures to an RSS feed. An additional option would be that it generates its own custom RSS feed so that you don't necessarily have to include the images as enclosures in the primary feed. I'd go the route of building a plugin versus customizing the RSS templates in WordPress because the RSS templates are a part of the core files and will be overwritten every time you upgrade.

I suspect your next question is: how do I build a plugin? Thanks to Miles, you won't have to start from scratch. There's another plugin in the directory that you can use as a foundation. If I were you, I'd download that and then watch this video about building your first plugin. I suspect you'll only need to do a few modifications to get it where you need it. Feel free to ask any specific questions you have about this process.

It is certainly possible with a plugin. The approach I would take would be to search the post content for the first <img> tag, and then put the source value of that as the enclosure.