With Flip Html5, you have updated a new and advanced skill of Office files producing! I guess a flipping presentation is much more persuasive than the old ancient PowerPoint Slideshow!
Let me show you the changing background files feature by steps:
1. Background Image:
You should have your own background file of Image in high definition and your own original files of PDF, Image or Office files;
Under Custom Setting panel, you can find background file setting to import your Image and Apply change to save the setting;
2. Background Sound:
In Search bar on the top of the custom panel, input the search keywords of "Sound", you will find the "background sound file" option. Here you can easily insert a background sound for your page flip book after save the modification by clicking Apply change button on frame of the main interface!