In addition to the official Demon Princes, Steve Jackson Games offers up a handful of other angels and demons that could be or become Demon Princes. Dark Khalid is the only “official” non-canon superior (he has a write up in the Revelations campaign cycle). The others simply have descriptions that would be consistent with being a Demon Prince, but they have never been acknowledged as such in the official materials.
First Calabite Prince of Destruction [deceased: killed by Lucifer]
First Calabite, and Lucifer’s rival for the throne of hell.
Habbalite Prince of Punishment
Camael was at one point the most senior of all Elohim. He was also the first of that Choir to fall. Assuming he survived the civil wars, he would almost certainly have ended up a prince. That said, there is so much punishment do administer in Hell, he and his servitors may not have time for Earth.
Habbalite Prince of Fanaticism
Formerly: This is the Fallen version of Khalid, Archangel of Faith
Revelations V p101
Calabite, Current Prince of Wrath (alt. Prince of Fanaticism)
Orifiel was Uriel’s senior Ofanite, and he fell when his Archangel was recalled. This much is canon. However, every other “most senior” angel who fell seems to not only have been offered a word, but a Princedom.