The Swiss Guard is the defense force of the Vatican, the smallest sovereign nation in the world and headquarters of the Holy See and the Roman Catholic Church. In a sede vacante period like right now, I was interested to know what flag the Swiss Guard uses when there's no pope. Sincerely, I couldn't find the answer; the only source I found seems to be dubious. However, I think it's interesting to show how's composed the flag of the Swiss Guard. Taking as example, the flag the Swiss Guard used by pope Benedict XVI from 2005 to 2008:
First, a pause to explain what's a Swiss guard: during early ages, kingdoms in all the Europe used Swiss mercenaries as defenders of their courts. However, the papal guard was the only that survived until our times, so it became THE Swiss Guard, and not only another Swiss Guard.
The Swiss Guard flag is square, composed by four cantons, divided by a white cross. In first canton, the coat of arms of the reigning pope (in the case of the flag above, Benedict XVI). In the sede vacante, this is the canton that cause doubts. On the fourth canton, there's always the coat of arms of the pope Julius II, that hired the pontifical Swiss Guard.
The other two cantons have stripes in the colors of the uniform of the guard. Now, a short explanation about the Swiss Guard gala uniform. The legend says it was inspired by a idea by painter and sculptor Michelangelo himself. The uniform was originally striped blue and yellow, the colors of the family of pope Julius II (Della Rovere arms), the same present in fourth canton. His successor, pope Leo X added the red, because his family (the famous House of Medici) colors were yellow and red. So, for about 500 years, it never was greatly changed again.
Ending the flag design, there's the personal coat of arms of then commander of Swiss Guard, that, on the time of above flag (2005-2008), was Elmar Theodor Mäder. Often a pope coexist with more than a commander, often a commander survives for more than a papacy, so the flag is changed more often than a new pope is elected.
Comments are welcome!