Technically, Kylorin was not given immortality but was made to stop aging. At least, that is what Kael said, but in the game (AoI pedia and the godslayer event) it seems more like he is an immortal who has aged considerably although slowly. Personally I'd rather him still appear to be in his mid 40s, with only a few streaks of grey hair at his temples instead of long silver locks. there is no need to change the leaderhead though, as it is closer to how he is most recently described in the game.
For everyone's benefit, since this stuff tends to get lost deep down in the lore forums

The students..
Was kinda thinking that the students would be the heroes.
As for an evil leader, i think the students all ended up being pretty evil, but I'd say gastrius or mikel dylantyr (fire was the most powerful and commonly used magic in patria at that time, right?) would fit well. That said if you wanted to include them as buildable units they'd be out of the question

Possibly have someone who 'resembles' the risen emperor? We don't know if he's actually ever been an emperor of patria but he might have been a strong mage with ambition at that time. Maybe death 'tames' his evil intentions as such.
Trenton Majosi was not evil. He may well have been the most noble hero of the age. I'd probably still say neutral rather than good though.
Fire was certainly not the most common magic in Patra. Rather, it was the most difficult sphere for mages to command. During that Age Bhall kept her precept firmly under her control and was a dedicated champion for good, so flames had a tendency to turn against any wicked man who tried to wield them. I wouldn't be surprised if at one point Kylorin made the use of flame a capital offense. Divine fire magic was widespread towards the end of the age and was quite powerful, but its main advantage was that few mages had the dispositions and discipline to learn to control it. Many mages instead turned to worshiping Danalin, in hopes that he would protect them from Bhall despite their wickedness. (The God of Water was by no means evil and would not protect the most wicked of them, but he was lenient enough that some not so nice magicians who avoided the more extreme vices might still get a modicum of protection.)
I would not be surprised if Mikel Dylantyr was one of the few students who sided with Kylorin in the rebellion. Of course, as he would have likely been trained to be evil earlier he probably always bore some serious burn scars from loosing control when he first tried to use flames for ill. It would not surprise me if he personally trained or was even the father of Menolly NuValle, the Queen and most powerful Archmage of the Bannor before the fall. It would also not surprise me if Mikel was among the friends of Kylorin whom Perpentach dominated and forced his old master to kill.
(I could see Carnivean joining him too, not because he agreed with him or was good or anything, but just because making the sides more even allows for greater carnage. Watching an empire burn to the ground is fun, but he would of course switch sides again by the time Good started to win.)
We don't know a lot about Gastrius, except that he was a student whom Kylorin killed for crimes far less serious than those committed by Perpentach, and that a copy of his mind lives on in The Momus as one of his greatest advisers. We can presume that as the master of Metamagic he may have been the most knowledgeable man who ever lived. Personally I've long (and with no real basis) liked to think that he was processed into the Demon lord Judecca, but I just thought of another (possibly cooler) possibility: Kylorin might not have actually killed him at all. It seems probable that he learned how to use the same sort of metamagic abilities as Gowlers do. It could be that all memories of his demise were fabrications planted to facilitate his escape. It could even be that the character of Gastrius never existed, but was a complete fabrication meant to distract those who had once known of the real master of metamagic. The one issue with this is an old pedia entry in which Agares spoke of his death, but he also spoke of Laroth's death and it has since been revealed that Laroth actually departed to the land of the dead while alive. Alternately, he may have allowed his physical form to be slain once he learned how to make his spirit dwell freely in men's memories. It could be that Perpentach's adviser is not merely a copy of a previously dominated Gastrius trapped in that one mind, but the real archmage who can now wander freely through the word of the memories of all mankind, bending the world of the percieved past as well as Laroth bends the dreams of the dead. Gatrius leaves open the possibility that all our lore comes from very unreliable narrators, and that we can blame Gastrius for any inconsistencies or mistakes Kael or I make.
Personally I tend to think that the only real ruler of Patria besides Kylorin should be Perpentach (who seems to have been not only a student but an adopted son and heir apparent), but he is already taken by the Baleraphs and is considerably different than he was in the previous age, when the voices in his head was blocked and he just had autism instead of multiple personality disorder.
I would suggest that the Patrian Capital be named Amur, to explain why the Patrians were canonically originally called the Amurites before Kael decided that was too confusing. Personally I blame Gatrius for this redaction, and still think that we should at least refer to those Kylorin led before uniting humanity into one kingdom as the Amurites.
I made her up, she's a Priestess of Tali
I don't think Tali has priestesses, an organized religion, or clergy of any kind. He is a chaotic and egalitarian deity, and those who revere him have lack the patience for any hierarchy. he has no temples, only shrines in remote and hard to reach places. The only sacrifices he wants is for people to entertain him through crazy daredevil feats and adventures.
The picture is nice, but I think she would make a better priestess of Ceridwen than Tali. Ceridwen's faith would have been the state religion for most of the history of Patria, although it was never popular except among the highest classes.