Image is part of your website and they are important. However, when search engines crawl your website, they don’t know what the image is about without having an “alt” tag. This tag is basically a simple description telling the search engines what is the image about or you can use keywords as well. So now you should check out your website and make sure all the images have the alt tag ready.
<img src="../images/xxx.jpg" alt="My Keyword">