You think your blog looks so plain and that you sure could use a new header image or background image for it? Or maybe you sometimes just want to add an image to emphasize your point? Times like these, you wish you had a camera and the skill to take good pictures. That or a bunch of images you could use. No need to worry though. There are various stock photos available online and you could find some of them through Yotophoto. It boasts of indexing over 100,000 stock photos. After entering your keywords on the search box, you would be given a results page with various images and you would be given information like the source of the images, the resolution and the license as well.
Just make sure that you read the license before using the images, ok? =) So you know if you should link back to the source, if you could use it for the purpose you had in mind and so on.