Recently I discovered a very nice feature in the image search in Bing.
If you drop down the "License" menu, you can select from several different types of licenses. This is extremely helpful when trying to locate images online that can be used for free. There is a lot of images in the public domain. Another good source is Getty Images which has a large collection of Creative Commons images and announced earlier this year (2014) that they were giving free embedding access to over 35 million images in their extensive libraries of images. Note that those images are NOT for strict commercial use, so you cannot get the images and use them as such, but you can link to them from anywhere (embed them) You can go to Getty Images' Embed Images search site and look for photos you would like to use.
Hope this helps someone in need for photos:)