I want to customise the email.php so that it looks similar to the website's style and the style of the newsletter. I want to include a couple of images (logo etc.) in the HTML email sent to the subscribers when they subscribe.
In the normal newsletter themes I use $theme_url to indicate the path to my images. However the email.php for subscription notifications is in a different directory, and there are no 'themes' to choose from in this case.
Where should I put these images, and what should I put in emails.php in order for the script to generate the right absolute links to them?