If you want to insert an image of your company seal or logo into a template, set the path to the image file: url('data:image/jpg;base64,<the_image_code_is_here>').
To generate the image code, use the special service Base64.
For example, to encode a file with an image, click on the "File" button and upload the image. Then press the buttons "Return text" and then "Send". The result is the image code.