when the app goes offline, it should display some text or built-in image

The current behavior shows that the app is aware of when it loses connectivity. It displays a small green notification (should be orange or red-ish, incidentally, since it's bad news).

But it should do a little more, in my view. I do notice that some views (notably if the main url is not accessible) just display an empty page with nothing on them. I think there should be an image or some text that could be configurable in the app for the app developer to add, as a default.

Start by tracing the existing offline connectivity notification and the views that become empty when the main URL is inaccessible. Determine how app configuration is provided, then define completion as showing configurable text or an image in those offline views, with the notification presented in a warning color.

Written by the indexing model from the issue text.