Add a image in header theme (path to link a image)

Describe the issue or problem
How can I add an image to a theme’s header? Im creating a subtheme of imersion theme.
Already I see there is this html code in header:

id="immersion_content_header"{if $immersionHomepageImage} style="background-image: url('{$publicFilesDir}/{$immersionHomepageImage.uploadName|escape:"url"}')"{/if}>

Work correct but I want to add a test image that does not depend on the user uploading an image. I will keep the original image like a commented line, but I want to see a image when someone install de theme, then in the readme I will add instructions to change it.

So my question (doubt) is: How can I add link to show a image in header theme?
may be in: /resources/dist/images (?)

There something like a /mytheme/resources/dist/images/imagebackground.jpg way to link to a image in theme¿

What application are you using?