I have successfully created a SAML service. Visiting the application URL displays the login screen along with the option to use single sign-on, which is great (see the attached picture). However, as you can see in the attachment, the icon is not rendered. The icon was uploaded as a binary file and configured as the "Provider logo" in the SAML Authentication Service, and the logo binary file is in a ruleset accessible to the Unauthenticated access group.
Here is the code in pyDisplayAuthScreenSelector that should render the icon: