This is the "On This Day" view, which automatically uses an image from your entry as the background. There currently isn't a way to set an image as a background except for viewing them in the "On This Day" view.

Awesome, John! 👏🏻 Guess it's time to update your Streak Story!

dayoneapp.com/blog/streak-...

Thanks for buying these, Adam! Please keep us posted on what you think of them. 📚

Thanks @donckrr.nl and sorry to disappoint! We're hoping to ship to Europe in the future.

Great question! Yes - on IOS and Mac, you'll find an entry's link by navigating to an entry's three-dot menu > Export > Copy Entry URL.