Speaking of stock art, how careful do I need to be with work I find that seems to be put online for general use, such as royalty-free image collections?
You need to carefully read the EULA, or End User License Agreement. A EULA may come in small print or in clickwrap, which appears on your screen when you install, download, or access software or other content online. When you click to accept the terms, you are bound by the agreement, whether or not you’ve read it. Shrinkwrap is a EULA placed in the packaging with the software; a shrinkwrap license typically will say that by opening the package, you have agreed to its terms. EULAs contain important, legally binding, and enforceable terms. They may prohibit making content available for downloading separately or prohibit using the image as part of another project.