Prior to deciding on what the new civilizations for the existing architectural styles would be (Spanish, Koreans and Huns) in the Conquerors Expansion, previously considered civilizations had been:
• Western European: Italians.
• Eastern Asian: Khmers and Tibetans.
• Central European: Swiss, Magyars, Slavs and Hasburgs.
In addition, the new architectural style was chosen to be for new world civilizations because the developers found the Aztecs to be cool, had name recognition, and had been defeated by a concatenation of lucky flukes.

Many of these scrapped civilization ideas would later be added into the HD Expansions of Age of Empires II.

An unused Trade Workshop building can be found in the game's data. It was originally planned to function as a building where to player could assign villagers to produce "Luxury Good", which could be sold for gold. Though scrapped, remnants of their existence can still be found in the game's scenario editor, with its icon resembling the Market economic building. The building can also be seen in several scenarios, too.

It's possible to extract campaigns from the game itself and edit them like Custom Scenarios.