In midrash rabah the symbol for shimon is given as shechem. The artists use the Damascus gate. However in the flags of the municipalities named for shimon in israel, the symbol is a sword and a pitcher of olive oil. Any idea where that come from?
ב"ה Shalom The creativity of artists isn’t necessarily dependent upon what is found the Torah or in the midrash, although some references may serve as an inspiration, therefore I cannot explain all aspects of what you have seen. The connection of the tribe of Shimon to Shechem and the sword is quite clear from the story in Bereshit when Shimon and Levy waged a battle by sword against Shechem because of what happened with Dina. All the best. Shana Tova