When clicking "add" and then databases, if you choose Postgresql you get a very brief "popup" with a link to documentation at https://docs.okd.io/latest/using_images/db_images/postgresql.html - this is a 404 link. 

    OCP 4.15.0

    Every time

Create new project, click "add", click databases, click Postgres and then select the documentation link.

    Actual documentation shows up that explains how to use/customize the image.