Atom or RSS2 feed and a product image

Question

Have a Ruby on rails site and want to use mailchimp's rss campaign. With it I need to send one image in the email.

At the moment, I can only get the image to display if I add it to (description in RSS) or (entry in atom) along with the description of the product. How can I get it to display on its own "Channel".

I tried this on the RSS (rss.rxml) feed but firefox nor safari would see it.

  xml.image do
    xml.link      url_for :only_path => false, :controller => 'products'
    xml.url       domain_host + product.product_image.url(:small, false)
    xml.title     "Test site"
    xml.width      144
    xml.hight      100
  end