When you launch the Vivaldi web browser, it shows the “start page” that contains the shortcuts to various websites in form of tiles containing the thumbnails or favicons of those websites. This is very similar to the way Opera web browser works, perhaps because Vivaldi web browser is designed by the same developer who once worked on Opera browser. On the “start page”, there is also a background image that can be changed to make it look more appealing to your taste. And Vivaldi makes it very easy to set any image as the “start page” background.
In order to set any image as the start page background in the Vivaldi web browser, all you have to do is right-click on that image and select Use Image as Start Page Background. That image will be now used as the background of the start page and you can confirm this by typing vivaldi://startpage in the address bar and pressing Enter. The newly set background should be visible on the start page now.
In case you want to reset the background image, then all you have to do is open Vivaldi settings, switch to the Start Page section and the pick one of the background images built inside the Vivaldi web browser. There are seven different background images are available. You can also choose a custom image from your hard drive for setting it as the background image.
Vivaldi is certainly a feature rich web browser that offers tons of options to customize how the web browser looks and works. You should give it a try and if you have not downloaded it, you can get it from https://vivaldi.com.