Like Odin said, it's a bit difficult given that most of them are good. I will have to go with The Sceptre of Deception one though; it works in a quite cohesive way with the album. Even though this can be said about most of the covers (except for the GvG one), this one stands out because of the conceptual connection.
Still, if we were talking about the whole "package", so far I'd be tempted to put Nortwhind as the forerunner.