Google image sitemap is a tool for Google to collect the metadata of the images you post on your website. After this, the images included in your content holds an identity of its’ own and can be highlighted out of the website meaning that a Google image search will be enough to find all the information and data related to it and it will eventually lead the viewer to your website, where the image originally belongs.
As an SEO tool, the sitemap will help in attracting more traffic towards your website if all the necessary details like title, geographical location, a title, description, and type of the images are specified and provided to Google by you.
Although the sitemaps on Google are created on the XML Sitemaps, it is advisable to create another XML sitemap for your website that will only contain the images and all the information related to them separate from all the other data.
This way Google will be able to read all that is there to know about the images. Regular search engines are not designed to crawl the images and therefore it is necessary to provide all the information of the images by the uploading authorities themselves.
The necessity arose in the first place because a lot of websites use only the text for their content and it sometimes get repetitive and boring for most people, as we all know a majority of humans are not very fond of reading.
Images are also a way to simplify a difficult topic. It is common knowledge today that images help people understand a topic much faster than plain text and websites are made to save time, not to waste it.
Creating an image sitemap is like creating another shortcut that will lead more and more people to your website. Unlike most of the other shortcuts, it is a legal and certified one that will never get you in any trouble.
However useful the image sitemaps are, they are not always necessary. There are times when you will do better without the sitemap and one of those times is when you have a smaller website that does not need it.
A website that is considered large often consists of more than 1000 pages and even a website with that many pages does not need a sitemap if it is changing the content on regular basis.