UPDATE April 2017: This post was originally posted in September 2014, and the world of free stock images that don't require attribution or a watermark has grown significantly since then. Enjoy the additions!
Unfortunately I am unable to offer my wallpapers without the watermark because too many people have turned around and posted my work elsewhere.
You can use any Pixabay image without attribution in digital and printed form, even for commercial applications. Just skip down from the first row, because Pixabay has a relationship (a clever one!) with Shutterstock, so if you want your images free without watermark, scroll a little.
Find the photo image that fits your blog post. Or, browse through images to inspire you to write! Many of these have a lot of “white” space, which is great for image-sharing sites, such as Pinterest. (Want to learn more about using Pinterest? .) So many of these images evoke a feeling, or a memory, or some sort of emotional response and are a great way to add personality to your posts. The best thing to do when browsing through these is to take the first one you like and download it, and get back to work. Because it's very easy to get stuck in the gorgeous rabbit hole of free images without watermarks, only we know that rabbit holes are not the way to turn a profit on a blog.