Sitemap Child Element

Hi Guys,


i have issue with create child element, 
Basically am trying to include product image in the sitemap. but i could not see the option for create child elements.

Anybody can you help me ??

<image:image>
      <image:loc>http://example.com/image.jpg</image:loc>
       <image:title>Image</image:title>
</image:image>