Posters and fliers: Professional grade images can really enhance posters and flyers that advertise holiday parties and other events.
"Wikimedia Commons is a media file repository making available public domain and freely-licensed educational media content (images, sound and video clips) to everyone, in their own language. It acts as a common repository for the various projects of the Wikimedia Foundation, but you do not need to belong to one of those projects to use media hosted here. The repository is created and maintained not by paid archivists, but by volunteers."
So before you download clipart off the internet, you need to determine what kind you need. For the classroom and basic computer programs such as Word, you most likely just need to get royalty-free raster clipart. If you need to use a high tech computer and software with a vinyl cutter, laser, or CNC then you need a vector clipart graphic. Either way you should use royalty-free clipart to be legal for commercial and other activities.