The image adds an entrypoint script that creates `/etc/pretix/pretix.cfg` from environment variables at startup. The file is only created if it doesn't exist or is empty; this means that you can still mount your own config file into the container as with the original image.
The script will fail and point out if required variables are not set.
You will need to look up the latest tag at https://hub.docker.com/r/pretix/standalone/tags and change it in both the `Dockerfile`` and in ``.gitlab-ci.yml`.