Isn’t a draw.io template and a background picture the same?
No, it’s not the same. With a template you can define a premade set of shapes and/or connectors from the template manager.
Background images or pictures in draw.io allow you define a template which can easily be applied to different pages without having to copy the same structure to each new page.
But, for a better understanding, please refer to this blog article Define Background images in draw.io
Fore more general info on draw.io for Confluence or Jira, please refer to our draw.io webpage.
And some more great blogposts! Blog - draw.io