[jalcaid001]

What is this used for?

I usually just configure 'background path'

[Hitcher]

Can you explain more as I have no idea what this is related to?

[jalcaid001]

I go to settings > Interface > Configure Confluence > Background

I can configure 'background path' and that will be the picture that shows on my main screen.
There is another option called 'background path master' that allows me to choose a file. But I have no idea what this file is used for.

[Hitcher]

That's for when the Master profile is being used.