Well, all right, you may have seen worse - this is, after all, the era of PowerPoint audience-abuse - but here's my experience from yesterday.
Picture this. We were sitting in a lecture theatre. Directly in front of us was a very large screen, at least 3 metres by 5 metres, covering most of the facing wall. It was brightly lit up with a slide of the outside of our theatre. We could focus on little else. Off to the left, in a dark corner, was one micro-lamp (on a lecturn) above the presenter's speech notes, reflecting enough light off the page for us to just make out his face. Huge bright screen, tiny bulb in a dark corner - the only sources of light. He talked about agriculture. The slide showed us the theatre - for the entire presentation.
Not one thing the presenter said had anything to do with the slide. Zero connection.
Worse. Think about how we humans take in messages from a presenter. It's well established that two thirds of us respond to visual stimuli more than any other stimulus. Less than a third respond best to sound. It was difficult for almost all of us to pay attention to the presenter's message. It was hard work.
Why it was a lesson for all modern presenters
Now, to the point - for all of us who do have relevant PowerPoint slides, but over-rely on them, turning our audiences into hypnotised chickens. Do you want your message to sink in?
Only show a picture on the screen when it specifically illustrates the point you're making right now. Then turn it off!
How? To turn the screen off but keep PowerPoint alive, create what I call a sleep slide. It's a slide that's all black. (Yes, just black, though it helps to insert a small mark in one corner so you can recognize it yourself.) Make the black sleep slide your number 1 slide and return to it (1, enter) when the relevant slide you're showing stops being relevant. So, you'll show nothing.
Yes, now the audience will turn and look at you.
Get over it. People sell ideas better than pictures. Wall-to-wall PowerPoint is audience-abuse and it kills the impact of your message. Surely a no-brainer.
For more on how to work with a sleep slide, see my blog Insert a sleep slide