To create a background image for the Oslo kommune website, you can use the @oslokommune/oslo-designsystem library. This library provides a set of pre-designed components and styles that can be used to create a consistent visual identity for the website.

You can include the design system in your HTML file by adding the following line:

<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@oslokommune/oslo-designsystem@latest/css/oslo-designsystem.min.css">

Then, you can use the classes provided by the design system to style your background image. For example, to set a background image, you can add the following class:

<div class="oslo-background-image">
  <img src="image.jpg" alt="Oslo background image">
</div>

Make sure to replace image.jpg with the actual file path of your background image.

Alternatively, you can use a CSS snippet like this:

.oslo-background-image {
  background-image: url('image.jpg');
  background-size: cover;
  background-position: center;
}

This will set the background image to the specified URL and scale it to cover the entire container.