Javascript Studio Pro allows you to customize the background and the opacity. while Javascript works on all windows device , Windows8.1, Windows10, there are different way to change it.
Javascript Studio creates a folder on pictures library called" JavaScript Studio Images" when it is installed.

Changing Background - Windows 10

In Javascript Studio for Windows10 you can change the background directly from the app.

1. Go to Settings and Tap Background Button
   
   
   
2. When the box options appears Tap Change button
   
   
   
3. Look for a picture you want and then tap Open
   
   
   
4. Set the opacity you like
   
   
   
5. Tap Save
   
   

Changing Background - Windows 8.1, Windowsphone 8.1

Changing Javascript Studio Background for Windows 8.1, you need to add images to "JavaScript Studio Images" folder that is created when Javascript Studio is Installed

1. Go to your picture library
   
   
   
2. Copy images in to the "JavaScript Studio Images" Folder
   
   
   
3. Open Javascript Studio
   
4. Go to Settings and Tap Background Button
   
   
   
5. When the box options appears Select an image you like
   
6. Set the opacity you like
   
   
   
7. Tap Save