[Galette-users] Local image path

Hello, First off I'm not a web developer, just a hobbyist trying to help a friend. I have managed to install Galette on a raspberry pi for an offline use and it's working fine. I'm attempting to make a custom page with custom styles, I'm using 'galette_local.css' for the styles but I'm having a hard time inserting a background image. I can't figure out which directory to place my images. How do I get the correct path? Merci.