I'd like a more personalized version of the offline page when the System Status is set to: Off. Is there a way to customize the page and/or change the text?
When the System Status is set to "off", Craft will return a HTTP 503 response, which will then automatically trigger the "503.html" template in
craft/app/templates to load, which is what you're seeing by default.
But if you put your own "503.html" in your
craft/templates folder, Craft will load that one instead. Same goes for the other HTTP status codes (400, 403, 404, 500, etc.).