The Extended Sitemap provides you with more flexible settings to work with the sitemaps correctly.
To access the Sitemap configuration, go to System > Configuration > Catalog > Google Sitemap > Extended Settings tab.
Screenshot: Extended Sitemap Settings
Include Product Images
Set "Yes" to add the image URLs into the sitemap.
Maximum Images per Product
Specify how many images should be added for each product in the sitemap.
Include Product Tags
Set "Yes" to add the product tag URLs into the sitemap.
Product Tags Frequency
Use this option to specify how often the product tags must be regenerated.
Product Tags Priority
Priority settings let search engines know what type of pages you consider most important for the crawlers to index.
You can add additional links to the sitemap.
Please use this syntax: /<url key>, <link name>
For example: /contacts, Contacts
Additional Links Frequency
Use this option to specify how often the additional links must be regenerated.
Additional Links Priority
Priority settings let search engines know what kind of pages you consider most important for the crawlers to index.
Allow to Split Sitemap
Sitemaps should be no larger than 10MB (10,485,760 bytes) and can contain a maximum of 50,000 URLs. These limits help to ensure that your web server does not get bogged down serving very large files. This means that if your site contains more than 50,000 URLs or your Sitemap is bigger than 10MB, you must create multiple Sitemap files and use a Sitemap index file. You should use a Sitemap index file even if you have a small site but plan on growing beyond 50,000 URLs or a file size of 10MB. (© sitemap.org)
Set "Yes" to enable sitemap splitting.
More information: http://www.sitemaps.org/faq.html
Maximum URLs per Sitemap
Specify the maximum URLs per sitemap.
Sitemap Split Size Limit, KB
Specify a maximum file size per sitemap in Kilobytes.
Submit Sitemap Automatically
Set "Yes" to submit sitemaps automatically.
Search Engines for Submission
Select the search engines to which you would like to submit automatically.