War Ensign of the en:German Empire from 1903-1919 (correction of date shown on image which shows 1918). Based on image of coat of arms at [1]. Currently unable to add further details for crown or further details to sceptor due to lack of high-quality images of the coat of arms.
The current version is based on this source Flags of the World - War Ensign 1871-1919 (Germany).

Originally from en.wikipedia; description page is/was here.
The original uploader was R-41 at English Wikipedia.