The Minbari are the only race, other then the first ones, that participated in the last Shadow War, as far as we know. This kinda begs the question - what other races could have participated? Certainly not the humans, who, 1,000 years ago, hadn't even taken to the skies. Probably not Centauri, either. The Narn might have, I suppose, but I get the impression the Shadows came to Narn - not that the Narn, themselves, took an active role in the conflict or even that they could (I get the impression they weren't space-faring at this point).
The Drakh might have (maybe, 1,000 years ago, they weren't minions of the Shadows). Maybe the Soul Hunters (would the Minbari, 1,000 years ago, have had the same disdain for the Soul Hunters that they do today?), the Ikarran (as featured in 1x04: Infection, although they're extinct), and maybe Varn's People.
Anyone else you can think of? And of those mentioned, do you think all of them actually would have participated?
I have to wonder if the Drakh, 1,000 years ago, were in the same position Earth was 1,000 years later - maybe the Shadows were secretly giving them technology in preparation to make them a servant race. Or maybe Z'ha'dum was, originally, their homeworld, and Lorien's presence was purely coincidental. Maybe the Shadows then took their homeworld over and enslaved them so they could be closer to Lorien.