Creating XML sitemaps for images and graphics requires tinkering with sitemapper configuration. Beyond that,
making image sitemaps for Google and other search engines is much like when you
create standard XML sitemaps.
With XML sitemaps for graphics and images you first need to make sure options include relevant image
file extensions
and
MIME types in
output filters.
To ease things,
A1 Sitemap Generator contains a
preset that sets all options to work optimal for image and graphic content websites.

Note: Even when using the
preset
button, you can still benefit from fine tuning options yourself.
One example is
output filters
which can help in cases where multiple page URLs contain references to the same image and graphic files.
When the website crawl has finished, all you need to do is creating the actual image sitemap file in XML for Google. Do this simply by choosing the correct sitemap file kind before you build sitemap:
You can configure how image sitemaps are built using options:
Create sitemap | XML sitemap extensions | Google image sitemaps | Ensure each image is only listed once
After submitting to Google Webmaster Tools wait a few days for Google to start indexing images.
You can view image sitemap details in Google Webmaster Tools by clicking on the image sitemap. Example shown in screenshot below:
Do note that
Google Webmaster Tools has a quirk since it always reports count of
<loc>...</loc>
and not the actual number of submitted images in
<image:image>...</image:image>. At least this was the case in March 2011:
Above is easy to verify by creating an image sitemap of one URL
containing two images. Google Webmaster Tools will only report one URL. It will not report count of images. Here is an example:
<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9" xmlns:image="http://www.google.com/schemas/sitemap-image/1.1">
<url>
<loc>http://www.example.com/</loc>
<priority>1.0</priority>
<image:image>
<image:loc>http://www.example.com/1.png</image:loc>
<image:title>image 1 title</image:title>
<image:caption>image 1 caption</image:caption>
</image:image>
<image:image>
<image:loc>http://www.example.com/2.png</image:loc>
<image:title>image 2 title</image:title>
<image:caption>image 2 caption</image:caption>
</image:image>
</url>
</urlset>
Some sitemap generator tools (not A1 Sitemap Generator) will try to artificially
increase the reported number of URLs in Google Webmaster Tools for image sitemaps by simply inserting
lots of page URLs <loc></loc> with no associated images <image:loc></image:loc>.
Therefore, to compare image sitemap tools and the number of included images,
you can try perform a search/replace of <image:loc> in the generated XML image
sitemap file. Most text editors gives you a count of found/replaced text items.
Do note that A1 Sitemap Generator automatically will attempt to leave out images
used as part of layout. (That is per Google guidelines for image sitemaps.)