Which slide should you change so that it reflects on all sides in your presentation?

For me, it would probably be the title slides if you can only change one slides.

Explanation: Because the title slides represent your presentation almost more than anything. Change your title slide into something that reflect on your presentation. For example, if you were doing a presentation on wolves, you should change your title slide's background or at least insert a picture of a wolf or something that has to do with a wolf. This way the people that you are presenting to would get a good guess on what your presentation is about based on your background or picture along with the title of your presentation. But if you were doing a presentation on the Greek Gods and your title slide's background is a pencil, people would be confuse. That why you should change your title slide so that it reflects on all slides in your presentation.

Try doing title slide.