Background Graphic instead of Static Color?

Fire App Builder documentation indicates App background can be changed to different colors here: https://developer.amazon.com/docs/fire-app-builder/optional-home-screen-changes.html

Is it possible, however, to use a background graphic image instead using a static color?
This should be an easy modification, no?

Start with the App background configuration described in the linked Fire App Builder documentation and trace where that setting is consumed in the Java app. Determine whether background images are supported and identify the relevant UI configuration or implementation area; done should mean the requested behavior is either implemented with a documented configuration or clearly ruled out.

Written by the indexing model from the issue text.