This is one of those “I see this all of the time…” things — slides with a patchwork of images of similar content when just one strong image would be infinitely more appropriate and powerful. Many of us seem to default to this pattern.
Maybe it is a byproduct of the slide designer/builder being unsure if they have the right visual. Or perhaps they are not confident they have stated their idea in the best way. He or she will add image upon image hoping that the repetition will help the viewer get it.
“Just one more will do it!”
In reality, it just dilutes the message. Your audience will quickly become weary of trying to see and process them all.
Find the one powerful, direct photo or illustration that tells your story in the best way (pay money if you need to — your presentation is worth it, right?) And then add just a few words to help the viewer identify the idea in their mind. Inserting extra photos (or extra words) because you are not sure if you have got it right just confuses the issue.