No I think that the placard announces things to the world, the grail is a purifier, the Athame can injure and kill that normally not susceptible and the Shroud to heal and resurrect. The Crown of Thorns, makes me think of Thorn Manacles for a god.
Presuming Jesus was Nemfected (one third of the White god) the Crown of Thorns contained him, the Athame pierced his side releasing Nemesis, the grail neutralised it, the Shroud resurrected him and the Placard announced to the world he was healed, creating a narrative of the crucifixion which has lasted two millennia.
The three nails were also to contain Jesus on the Cross and generate the suffering which seems necessary to drive Nemesis out. It is posited in PT that the nails in the swords contain an angel, the five artifacts are an order of magnitude greater than them, so multiple angels, archangels or other powerful entities powering them? The Placard announced Christ as King of the Jews, the Swords are wielded by descendants of kings.
Harry I think is using the Athame in the battle, and the Placard after the battle to announce to at least Chicago that the Supernatural is out there in a way which cannot be dismissed. Alfred was somewhat non-pluses as to his choice of the placard. The line about what Harry did after the battle would suggest this, as would the line in PT that things are not going to be the same.