I've taken this picture during my holiday in Spain.
As my knowledge of ancient weaponry is boosted by EB, I guess those weapons are thracian/getic (falx, rhomphaia), composite bows are sarmatian, shields are celtic and the helmets are thracian/greek. The thing I don't know is why the Romans created such sculpture. Maybe it should portray the weapons of defeated enemies or the weapons of thracian mercenaries.