When I speak about the art of creating presentations and pitch decks, I recommend using full frame, legally yours, images as part of your slide deck. What you can do in school as a student is different from what you can legally do as a professional.
Full frame gives your slides have more punch. They have more impact than what we typically think of when using PowerPoint. When you do a google search for images, it’s like going to the library. Screen grabbing an image doesn’t make the image legally belong to you. It’s great though, for researching. Sometimes your google search will take you to stock sites where you can buy the image. I recommend using professional photo stock sites. They have great search abilities that make it easier to find exactly what you want. This will save you time, and you’ll know that you have a legal license to use the image once you purchase it. Avoid using photos that say “For Editorial Use Only.” Free image sites are less reliable in many ways.
Shutterstock.com and Adobestock.com let you search for images right inside of PowerPoint. You need to have an account for payment. Add this feature through the Insert/Store menu, or you can go directly to the stock photo websites and download them from there. When an image has a watermark across it, it’s intended to be used as a placeholder until you’re sure it’s the right image you intend on using. Bigstock.com is sometimes less expensive, but more dated. Great for less expensive vector maps. Getty has higher priced photos, which could make your presentation a bit more unique.