As of 2014 or so, BahnCards do not carry the card's holder photo anymore, see here: https://www.bahn.de/p_en/view/bahnca...hncard50.shtml
According to this website you could even purchase a provisional BahnCard online and print it at home, so no need to worry about getting it mailed to your adress.

As mentioned before, basically a BahnCard is not transferable. If purchasing an online ticket the name of the ticket holder is printed on the ticket, and it should match the name of the card holder. Any misuse becomes obvious quickly. Tickets bought at the counter or at ticket machines do not have any names on it. If a passenger produces a valid ticket and a valid BahnCard on the train it is very rarely that conductors ask for additional verification or identification. The conclusion to draw is up to you...