Bull. Those German ballots may come with names on them, but you can also strike out names and add other names by hand. There may be individual restrictions on whether you can only name people that registered as candidates, or anyone fulfilling the legal requirements for being a candidate, but writing a name on a ballot doesn't always make it invalid (of course, if you write something else than a name - say, a story or an insult, or of you draw faces or doodle on it, it does become invalid).
OK. My version was the cautious story, if you want to make sure your vote counts. I never bothered testing the limits back home --- also you do not really get feedback, your vote will be just silently discarded or counted.
By the way the Bundeswahlgesetz (Paragraph 39, Absatz 1) says: "Ungültig sind Stimmen, wenn der Stimmzettel [...] einen Zusatz oder Vorbehalt enthält."
So in general, putting extra stuff besides your tick, is not allowed.
