It isn't whether one is good or bad that determines there fate in death, only what god they served. If one did not serve a god in life, he will go to Arawn's underworld, where all mortal souls were meant to go and where I think they may have all gone before the compact. I believe that Kael has stated that even in the Age of Rebirth a large majority of souls still find their way to rest in the Netherworld instead of the vault of a god they served.
One's experiences in the Netherworld are like dreams created from one's own subconscious, and are meant to give a departed soul the reward or punishment that deep down it thinks it deserves. Innocent children often find the Netherworld just as pleasant as any heaven (probably excluding the True Heaven, but only the gods have seen that so mortal souls don't know they are missing anything), while the wicked may find it worse than many hells. Of course, some people are too hard on themselves and others are too easy, but no one can blame his estate in the underworld on Arawn's judgment. (Also, some things may have been thrown off by one evil denizen of the Netherworld who convinced his subconscious that what he deserves is Godhood...)
Note that many worshipers don't realize that they are worshipers. Almost all who serve Mammon fit in this category, so finding oneself in his city is often a shock. There is little doubt that many Grigori end up here, along with even more Hippus.
The evil gods have managed to claim a few souls that don't belong in hell though. It isn't entirely clear how, but perhaps they've managed to argue that souls that were indecisive in choosing a god were in fact showing a laziness that means they served Mulcarn's sphere. Kael originally said that most souls in hell skipped Mulcarn's vault and went straight into Mammon's, but he changed that to having Mulcarn's vault be a massive filter through which almost all souls must pass and where the majority of souls in hell are still waiting to be processed. It may be that most of those who belong in hell go to Mammon's vault first and that most of those in Mulcarn's vault should really only be in the Netherworld.
Edit: Weird, my computer randomly restarted itself almost as soon as I posted this. I wonder why.
The Luonatar would probably go to Arawn. Their loyalty to The One would probably stop any evil god from laying a claim to them like they could others destined to the Netherworld. I suppose there is also a chance that those who discovered the truth of the One Creator might spend some time with the God of Truth (Lugus) while waiting for his return, or that their zeal not to follow any of the false gods could give them a commitment to balance enough to make Dadga's vault their waiting room. (Of course, I have a suspicion that Erebus may actually be Dagda's vault, as it was created to manifest all precepts in balance and as I don't think a plane made entirely of balance makes any sense. Perhaps most importantly, the history explicitly claims that he was the only god to refrain from making his own plane before they all came together to make Erebus. The worlds the gods made before Creation and their current vaults may not be the same thing however (although I believe that Agares' hell was made from Nyx), and he could have created his own world after Erebus.)
We don't know for sure that Dragons have immortal souls that would go anywhere, but if they do then surely they would go to the vault of the god who created them. Most dragons are very close to their makers, although I suppose some might have fallen and joined other gods like some angels did. Of the one's we know, only Acheron would even think of disobeying his lady, and he turned evil before she did so he might even have returned to her service after she fell.