Stress-inducing cover image?

A frightening, dramatic, stressful image can greatly enhance your message. But I would not use it on the cover page of your presentation. That page usually sits on the projector for a long time while the audience is walking in and you do not want to destroy their mood before your talk started. Use the stressful slide at a key moment inside your deck instead, it could even be one page 2, just not on page 1.