What is meaning of image sitemap and its importance? How can I prepare if I want to create for my site? Should I prepare image sitemap for any site as generally we prepare sitemap.xml?
Image Sitemaps can highlight the important content on a site and allow crawlers to quickly discover it. Sitemaps, as the name implies, are just a map of your site - i.e. on one single page you show the structure of your site, its sections, the links between them, etc.
You may read this help article by Google about image Sitemap http://support.google.com/webmasters/bin/answer.py?hl=en&answer=178636 Hope this helps!