sorry for the inconveniences.
The image replacement is used when you use a video background. What background option do you use? Image version?
Anyway I can help you to resolve the problem. I can modify the plugin for you to get you want.
I don’t know why it doesn’t work correctly. I did tests and the plugin modified worked fine.
Could you create a new user for me in your admin panel? In that way, I can check the code and change it. I have done thi with other users, so you can trust me.