You will need to override the Ananke theme’s template and provide for a way to pick up an image from within a Page Bundle to be used as a featured image.
For example you can name the desired file so that it contains the word featured and then in the template use something like:
{{ $img := (.Resources.ByType "image").GetMatch "*featured*" }}
See this topic for more: Displaying Featured Images
Also see more about the GetMatch method over here