What is Internet Bumper Stickers?
Internet Bumper Stickers [internetbumperstickers.com] is a humor website featuring hundreds of "bumper stickers" as digital images, organized in multiple categories.
You can use these stickers for free in your own website so long as you follow the license. As of writing, the stickers are licensed under Creative Commons, Non-Commercial, Non-Derivative. This means you can't modify the stickers, except for resizing them, and you can't include them in a sold product. In particular, this means you can't republish the stickers in your blog if you monetize the website with ads.
Observations
Am I a Pirate?: I'm not sure if there is a way to take a screenshot of the website without the screenshot featuring the stickers that I'm not supposed to be copying into my commercial website. Screenshots are often copyright infringement, even if it's a screenshot a GUI, but I don't think anybody has ever been sued for taking a screenshot.