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

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.

Prior to deciding on what the new civilizations for the existing architectural styles would be (Spanish, Koreans and Huns) in the Conquerors Expansion of Age of Empires II: The Age of Kings, 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.

During development, Wolves were meant to have much more complicated behavior. Every new match would have wolves start the game by forming a pack and then wandering across the map, seeking food sources while avoiding towns. Their level of aggression would vary based on their level of hunger. Furthermore, players would be able to hear howling in the background at points, the frequency of which would hint at the threat the wolves posed.

Despite being largely forgotten in favor of its sequels, the original Age of Empires remained popular decades later in Vietnam, due in large part to pirated copies of the game being bundled in Vietnamese computers and a long history of LAN matches dating back to the 1990's. Modern Vietnamese players often use custom rulesets, and top players have earned tens of thousands of dollars in tournaments viewed by audiences as high as the hundreds of thousands.

In 2023, this popularity in Vietnam was formally acknowledged by Forgotten Empires, the modern developers of the series, in their "Return of Rome" expansion for Age of Empires II, which ported and updated content from the original Age of Empires to Age of Empires II: Definitive Edition. The expansion included a new faction, Lac Viet, "in honor and recognition of ["The Rise of Rome" expansion from the first Age of Empires game's] phenomenal popularity in Vietnam."