Blurb doesn't review, edit, or monitor books and Wall Art as they come through, and we can't advise on whether it's legal or "safe" for you to use content you've found on the internet or elsewhere. Using copyrighted material without the right to do so violates our Terms and Conditions.
The World Intellectual Property Organization also has some excellent FAQs on copyrighted material under the Using other people's work section.
Remember, the content is entirely up to you, the author. We don't review, edit or monitor content and we will investigate any complaints of copyright infringement.