Notify comes as a package with 6 Notification mails, you can easily drag&drop or hide the ones you don’t like and export this file.
In the Themebuilder in the left menu you’ll see 6 tabs numbered from 1/6. Choose your Notification Email and style it with this tab.
Use the top button “Change background images” to change your background images.
Gmail doesn’t support CSS for background images so the bg image can’t stretch in their system. To fix this: upload a large background image (ex. 1800px width)
Outlook doesn’t support background images, in their system you’ll see a solid background color or your choice.