Generate a URL to a background image from a label and output that to a style tag in the head (Liquid).

_random-image-style-tag-liquid.html

{% assign background1 = site | first_random_image_tagged_with: label: "backpage-1-hero" | image_url: size: "1780x580" %}
<style>
  .example {
    background-image: url('{{ background1 }}');
  }
</style>

<!-- OR: -->

{% assign background2 = site | first_random_image_tagged_with: label: "backpage-1-hero" | image_url: size: "1780x580" | css_background_image %}
<style>
  .example {
    {{ background2 }}
  }
</style>