In the Warcraft III Reign of Chaos beta, the Gryphon Rider's portrait showed the face of the Gryphon, but its quotes were those of the Rider, making it seem like the Gryphon is the one speaking. This portrait was replaced with a distant shot of the world model. It also had a special texture, "GryphonRiderPortrait.blp", that was removed.
In Warcraft III The Frozen Throne, a golden version of this texture, named "SiegeEngineHead.blp" was added and was used for the Siege Engine and Wagon models. If you change the Siege Engine model to use the Gryphon head or the Gryphon Rider Portrait model to use the Siege Engine head, the textures are swapped perfectly.