When you use a relative path like /some/path/here.jpg, and you are on www.example.com, the browser will look for
www.example.com/some/path/here.jpg
Which doesn’t exist. But you might have noticed that you can use relative path in a CSS file. That’s because the path is calculated based on the location of the CSS file, while in your case the images are being calculated based on the location of the current URL.
The main CSS file of your theme is located at your-theme/style.css. You can build relative paths within your stylesheet, for example you can use ../imgs/whatever.jpg in your CSS file to point to wp-content/imgs/whatever.jpg. However, storing any file outside upload directory or theme’s is not recommended.
What you can do, is to use core functions to create a full dynamic path. For example get_template_directory_uri(); will get the current theme’s path, so you can use in your image’s src:
src="https://wordpress.stackexchange.com/questions/276705/<?php echo get_template_directory_uri();?> /imgs/whatever.png"
To get the wp-content‘s URL, you can use content_url();.