The FBI flag in \units\payday2\props\stn_prop_lobby_flag_fbi has 2 different versions the default one is from the Sicherheitspolizei but I also have created an option with the SS flag, both have a preview picture if you want to use the SS flag instead of the default one just rename or remove the file named "stn_prop_lobby_flag_df" and change the name of "stn_prop_lobby_flag_df SS alternative" to "stn_prop_lobby_flag_df" so the game uses it instead