layout_bg-8.x-1.0/layout_bg.layouts.yml

layout_bg_onecol:
  label: 'One-Column Layout with Background Region'
  theme_hook: layout__layout_bg
  library: layout_bg/layout_bg_onecol
  class: '\Drupal\layout_bg\Plugin\Layout\LayoutBgOneCol'
  category: 'Columns: 1'
  default_region: content
  icon_map:
    - [background, background, background, background]
    - [background, content, content, background]
    - [background, content, content, background]
    - [background, background, background, background]
  regions:
    background:
      label: Background
    content:
      label: Content

layout_bg_twocol:
  label: 'Two-Column Layout with Background Region'
  theme_hook: layout__layout_bg
  library: layout_bg/layout_bg_twocol
  class: '\Drupal\layout_bg\Plugin\Layout\LayoutBgTwoCol'
  category: 'Columns: 2'
  default_region: first
  icon_map:
    - [background, background, background, background]
    - [background, first, second, background]
    - [background, first, second, background]
    - [background, background, background, background]
  regions:
    background:
      label: Background
    first:
      label: First
    second:
      label: Second