Google has updated the image search to allow you to search for images that are free to use on your blog. The images search results can now show images that have been tagged with the Creative Commons license and it is also capable of returning content under other licenses such as the GNU Free document license.
To get this feature when you are searching go to the Advanced Image Search page then under the usage rights section you will see a drop down with different types of license that you can search for. “You’ll still have to verify that the licensing information is accurate We can help you take the first step towards finding these images, but we can’t guarantee that the content we linked to is actually in the public domain, or available under the license,” Google states.