What are accessible Images?
Images present accessibility issues because they are inaccessible to blind people and vision-impaired people. Because this is a reality, you need to make sure that if you use Images at all on your Web site you are also including text descriptions of some sort or even equivalent text versions of your content on a separate Web page.
Another issue arises when you use pictures or Images because Web crawlers and Search engines cannot "see" the text contained in Images and cannot tell what an Image represents. Because this is true, you should follow one of Google's Design and content guidelines which is to:
Try to use text instead of images to display important names, content, or links. The Google crawler doesn't recognize text contained in images. - Google
If you must use a picture or an Image on your Web site or if you simply would rather use Images to represent products and/or services then you should use the "alt" property of image tags for your Images to describe what the picture or Image represents.
Example:
<image src="rabbit.gif" alt="Rabbit" />
The "alt" property of an image tag is used by screen readers, Web crawlers, and Search engines to index your pictures and Images. You could also choose to use the "title" property to describe your picture or Image (though some Web browsers do not support the "title" property for an image tag).
Example:
<image src="rabbit.gif" alt="Rabbit" title="Rabbit" />