List of unnamed Thunderians
These two guards were encountered by Lion-O when he traveled back in time and space to Thundera. They assume the adult Lion-O who declared himself Lord of the ThunderCats was a Plun-Darrian impostor since Claudus is the true Lord and his son is "but a boy", but allow him to pass when they see him wield the Sword of Omens, not before giving him a warning of the next earthquake. ("Return to Thundera")
Upon the recreation of Thundera Thunderian refugees from across space returned home. Most are unseen and do not have names. Three unnamed refugees arrived on Baron Tass' ship, they were escorted to a thunderian settlement by Wilykit.("Well of Doubt")
When Torr came to New Thundera he brought other Thunderians with him. They are presumably his family, this group was captured by the robotic Two Time and was freed by the ThunderCats. This group includes himself, woman, a young male, and an elderly woman.
Leah's parents were part of a group of refugee ships returning to New Thundera, the group had at least five ships, but the group was caught in a meteor shower, Leah and her parents were forced to eject from their ship in individual escape pods. Its unknown if any other ships had survivors.
Amortus had many victims turned to stone within the Land of No Return that all appeared to be Thunderian, dozens, perhaps many more. Lion-O was able to animate them with the Sword of Omens so they could fight against Amortus, knowing he could no longer harm them since they were still made of stone. They triumphed against him in battle, what happened to them after is currently unknown.
Wielder of the Totem
This unnamed Thunderian from some point in the past seems to be a Thundercat He wears the symbol of the organization. He used the power of the Totem of Dera to bring to life a rock formation. This Thundercat is unnamed and only seen in the pool of Mumm-Ras lair when the ancient spirits of evil explained to him how the Totem worked.
Malcar's new family
At one point Lion-O envisioned the gathering of his people to return to Thundera, he imagined hundreds of people being gathered to return to their now restored home. He considered the knowledge they would have all gained in their time away for Thundera, it is unknown if any of these events represented things to have actually happened, or if it was all Lion-O's imagination.