magento2 – How do I add images to custom themes?

I have to add an additional static image in the page header. Right after the logo.

My child topic tree in
(magento project root)/app/design/frontend/My_Vendor/My_Theme/

  ├── Magento_Theme
  │   └── templates
  │       └── html
  │           └── header
  │               └── logo.phtml
  │               
  ├── media
  │   └── preview.png
  ├── registration.php
  ├── theme.xml
  └── web
      └── images
          ├── logo.png
          └── CUSTOM_TAGLINE.png

The CUSTOM_TAGLINE.png missing in the static files, the rest works fine.

Symlinks to images are created in a static folder (magento project root)/pub/static/frontend/My_Vendor/My_Theme/my_language/images/, My custom logo.png appears there together with loader-1.gif what I suspect comes from the parent topic. Unfortunately my custom picture CUSTOM_TAGLINE.png is not there.

In my modified Magento_Theme/templates/html/header/logo.phtml I have the lead echo $block->getViewFileUrl('images/CUSTOM_TAGLINE.png') This works as expected and returns the path to the generated static folder.

What do I miss here? Do I have to declare that? CUSTOM_TAGLINE.png somehow?