Recently, SharePoint Online/O365 (and soon SP 2019?) released an upgrade to the page title area of modern pages. Previously, the header area of a page was restricted to a banner image and text. Then they released an update that allowed customizing the image. Then removing the image. Now we’ve leaped ahead and you can choose from four layouts:
First edit the modern page and click the “Edit” icon on the title area:
Select a layout & alignment
Image and title
Plain
Color block
Overlap
Add “tag” text above the title
Show published date
Don’t forget to save your changes and publish your page when finished.