Open Trivia Game layer and on the right side bar click Style.
Now select the Trivia style you like.

In Elegant design, you can make your Trivia Game layer transparent, so your background becomes visible. You can use an image, video or a webcam view as a background.

As an alternative, you can also select individual designs for each screen (Start/Question/Question End/Game End) by accessing Game Appearance Config and uploading images.