Image Sitemap Explained
How to create Image Sitemap
To provide Google with information regarding images on the website, the site owner must add relevant details to the standard Sitemap. This includes the type of image, subject matter, caption, title, geographic location, and license. The process enables site owners to identify which images on each page are most important.
Sitemap Generator script will include unique images URLs in sitemap to avoid duplicating repeating images for all pages. Images sitemap is stored in a separate xml file.
An example of Images sitemap file on our site: sitemap_images.xml
You can find more details on google webmaster tools help pages.