When Chrome 68 rolled out, users spotted a flag named “New Tab Page Background Selection” in chrome://flags but enabling it seemed to do nothing.
However, when I tested this in Chrome Canary 70, a settings icon appeared in the bottom right of the new tab page.
However, it could not be clicked. It turned out that the icon is blocked by an element of id “most-visited”. So, I opened Chrome DevTools(by pressing F12) and deleted the element.
Now, the settings icon was clickable. Clicking on the icon showed the following dialog :
The dialog box included options of Choosing backgrounds from Google Wallpapers (yes, like the android app) or a local image. I decided to test the Google Wallpapers.
Then, I clicked done and volia !! The background became the page background. The background did remain after opening another tab.