A lot of libraries like to add "terms and conditions" to their self-registration pages. I typically add this using Javascript, but it would be a lot nicer and easier to use a HTML Customization so that libraries could write this themselves.
There is PatronSelfRegistrationAdditionalInstructions and Bug 19838 - Add system preference for adding text to self registration form :) *** This bug has been marked as a duplicate of bug 19838 ***