If you own the images used in your posts, you may want to license them with Creative Commons and notify it to Google: now you can do so via Rich Snippets, instead waiting for auto-discovery.
First of all, I suggest you to have a look to my tip on get ready for RDFa, where you can find useful information on enabling them for your blog. Once you have changed your DTD, you should go on reading.
This method is valid for Google Image Search: of course, you could specify other license types; Creative Commons is just an example (and it allows you to add a RDFa specification).
Below, I show the Google’s standard way to implement licenses — on blogs could be preferable to use an inline alternative I’ll explain after:
<div about"/path/to/image.ext"> <img src="/path/to/image.ext"/> <a href="http://creativecommons.org/licenses/by-nc-nd/3.0/" rel="license">Creative Commons Attribution - NonCommercial - No Derivatives Works 3.0</a> </div>
This is what Peter Linsley explained on the official Google Webmaster Central’s blog: you can watch the related video on YouTube too. I’ve just moved the rel attribute in the end to fit the W3C’s standards.
Anyway, blog posts should contemplate paragraphs and this markup could break your layout. So I used these attributes on different elements to avoid issues.
<img about="/path/to/image.ext" src="/path/to/image.ext" href="http://creativecommons.org/licenses/by-nc-nd/3.0/" rel="license"/>
The about attribute could be inserted in almost any HTML element and the href attribute isn’t “clickable” so you may include the image in an anchor, if you want to.
My way applies especially if you use WordPress’ thumbnails: providing a working link to the license’s text isn’t mandatory (and search engines will do it for you).
