Re: creepy idea of the day
"We could get to the situation in the future where having a JPG on your pc is a hot potato."
No, we couldn't. There are so many images used by programs and websites that there's no way of figuring out which of the thousands of images you care about. No, they're not going to make an expensive, likely cryptographic, format for your desktop icons and video game assets. Oh, and video frames too, because if you don't stamp each of those, people will put their pictures in one and have users run it like a slideshow. That adds complexity and size to anything that reads or writes image data. You might as well ask for mandatory KYC on all text, which isn't going to happen either given how often you use the same text as other people.
"Think how much easier that is to detect by outsiders"
It's really hard to detect. You have several existing formats to detect, which requires a full scan of the user's disk, which the user is likely to dislike. When you've done that, people will immediately invent new formats to get around that. It is a 2D array and disks are big--it's not hard. You're now playing whack-a-mole with format designers. That's without considering pictures embedded into programs which display it when run (if you just set pixels, it will look like text). Then steganography to hide it in something else. Then programs to retrieve the correct bit pattern from another file which isn't signed.
In order to reach step one, you already need something a lot more invasive than has ever been tried. It's not practical. In your title, you left out two words. It didn't win the prize for creepy idea of the day--Apple's got a monopoly on that whenever they open their mouth lately. It won for creepy and useless idea of the day.