We could have a copyright attribute, with a link to the licence, could be useful for giving extra information to plugins or external sites.
<img src="landscape.jpg" copyright="https://creativecommons.org/licenses/by/2.0/" alt="landscape" />
Not only for images, but for all elements. Like articles or code blocks.
<pre><code copyright="http://opensource.org/licenses/cpl1.0.php">
if (false) {
var foo = "bar";
}
</code></pre>
Why?
External sites or plugins could make use of it when checking images or articles if they are allowed to use it.