The cross. The cross is not an idol, nor should it be an idol but it is a reminder of the sacrifice that was made for us.
There is no Protestant symbol, because Protestantism is a loose connection of denominations with roots in the Protestant Reformation, not a single organization.
Usually just a simple cross
protestant
Apostle Mark's symbol is the lion. You can read more about it on the link below since I am a protestant theologian not a Catholic one.
This monogram standing for "Iesus Hominum Salvator" (Jesus the Saviour of Humankind) is used in Protestant churches as much as in Catholic and Orthodox ones. As is the Chi Rho sign (that looks a little like a P and X superimposed) - the first two letters in Greek, of Christ's name (Ch - R) - and also the Ichthus - the symbol of the fish.
Prince William of Orange, a Dutch Prince, -later King William - led the victorious Protestant forces against the Catholic King James at the Battle of the Boyne in 1690, so most Protestants choose the the colour as their symbol.
Light is often referred to, in Catholic and Protestant, as Jesus. b/c Jesus is the light of the world. He is the light in the darkness, the only hope of the world. :D
He was a protestant.
Protestant
Protestant
Protestant missionaries. -APEX Learning®️ 2021
Protestant.
Protestant
Protestant.