Our Branding team are going to have a meltdown over this. This is another example of Microsoft trying to be helpful but causing real headaches for organisations that have basic standards around branding and UX in place. Please ALWAYS include a switch for admin to turn these sorts of features off. For context, I have worked with SharePoint since 2003 in six different organisations and this would not be welcomed by any of them at any point.
This would only be useful if we can create our own designs using our branding only and use our Org Asset library before stock images.
Do Microsoft actually run their ideas past SharePoint admins at "normal" organisations? I'd happily take part in such a panel or vote in a forum as to what the real world sees as priorities for development. I'm aware there are ways of voting for features and fixes but that tends to be to resolve existing issues raides by users rather than voting on solutions that are instigated by Microsoft don't seem to address a real problem.