Images used in websites have a serious keyword value when they are used right.
There are 3 variables, which we think of, can show search engines what the image is about? These are title, alt, and the image name. Matt Cutts, the head of Google’s webspam team describing us which ones are important in this video:
What is alt attribute?
The alt attribute is used in HTML and XHTML documents to specify text that is to be rendered when the element to which it is applied cannot be rendered. In HTML 4.01, the attribute is required for the img and area element types. It is optional for the input element type and the deprecated applet element type.
