Hello there

I'd like to create over 10 presentations and each will include over 50 slides. In addition I need to update them very often in the future.
For visualization I'd like to put a progress bar on each slide. Progress bar includes graphical elements not just text information, so I'm prepared to create each step with a graphical editor.

My question is: Is there a way to create a theme or template which will include automatically the correct background based on the page number?

Of course I can do it manually for each slides to select the proper image, but it gets difficult once I need to swap some slides or just delete one and I need to edit all remaining slide with correct image.