Hello Sandor,
I´m glad you like my painting.
I have done some research on standards of the early 16th century and it turns out that many, nearly all european states uses religious symbols in their standards. Most come was the virgin Mary, some saints or like here the crucified Jesus. I would not show the standard of a certain regiment but the armour of the horsemen is mostly Spanish so I put Jesus on a red ground, red is a colour used by the Spanish in those days.
But you are right, I have seen some swiss colours of that time with religous figures on them.
Christoph