Too many speakers are lazy and look for stock photos to use in their PowerPoint presentations. Although stock photos are available on all topics, they aren’t personal.
For example, if I were speaking about Pugs (a topic near and dear to my heart) I could find a zillion photos of Pugs to illustrate my talk. However, using the photo of P.J. would make it special. I could explain that I took it more than 25 years ago, when P.J. attended his first dog show. [He didn’t do very well that day, but did eventually become an A.K.C. champion!]
If possible, use your own photos! It will help your presentation be unique and personal.