It looks that Microsoft is testing more tight Bing integration with Windows Search. For some of the Insiders, the Search flyout in Windows 10 now shows Bing's Image of the day.
Here's how it looks.
As you see, the feature replicates the appearance of what you can see on the Bing home page. It even includes an image overlay that reveals the place and other photo details. Similar feature can be also found on the lock screen in Windows 10.
It is not clear if this change is planned to be rolled to the public, or it is a placeholder for something more important that we will see in the near future. Personally, I don't see the change here (yet?).
Microsoft is actively working on the Windows Search. It constantly receives both major features and minor improvements. Just recently it was updated with the Dark theme support.