The Field Group Module allows you to use tabs and accordions for your field structure, for the input and output modes. The Field Group Background module allows you to set a background, without using any CSS.
You need an image field in your content type. For each node you can use another background.
This is an example of a display of fields. Choose a GROUP field, background image. Put it above the places where you want to apply the background. Important!. The real image field you can hide. (see below)
Configure the Group Field and Ready.