Notifications and email alerts do support some limited customization. 

You can change the Header, Footer, and company name in the message. As well as upload an image that displays in the top left corner (usually your company logo). The body of the message, however, is static. It will only display in english and cannot be changed at this time.

Additional customization features are on our road map. We look forward to adding localization and other languages in a future build.