Whenever Brave is launched, the homepage (new tab) is shown with either the default background or sponsored rotating backgrounds.
A lot of users don’t like this and have been requesting a way to add their own pictures since mid 2019 or earlier.
Adding a feature where users can display a custom background (either by link or uploading a custom picture) is really not hard to implement and doesn’t take long.
For example, turning off background image on the dashboard displays the default purple-pink-orange-tri-colour background. A link or a file displays this. It’s not hard to enable users the option to modify it and replace it with their own.