Is it permissible to continue publishing on a religious page that is thought to be private to a famous preacher, knowing that the page is not affiliated with him and only publishes his sayings and pictures?

It is permissible to publish the sayings and news of a specific preacher on a web page, as long as the page is not named after him and does not claim to be his. It is preferable to name the page "Admirers of so-and-so" to avoid confusion. The Shari'ah encourages the dissemination of good, for whoever calls to guidance will have a reward like the rewards of those who follow him.