BUT the slide show is sneaky.
I will be changing the theme once in a while, but the one I have running right now is a series of coloured illustrations of an owl sitting on a branch. It's eyes appear to change position. There's a branch in behind that occasionally makes an appearance. Even a bit of text sometimes shows up.
I never mention it to people. I just let them second guess their own sanity when the picture isn't always the way they remember it compared to other times they looked at it. I'm really abusing the fact that it doesn't look like a computer screen here.
Although it is completely unrelated, my inspiration came from remembering the Johnny Castaway screen blanker from back in the 90's. It was based on random "skits" that appeared to tell a story.