Hm, okay. I've fiddled around with world anvil a bit to do some worldbuilding for a tabletop setting of mine but not nearly as much as your friend. Generally though I'd say how you approach it should be dependent on your goals for the project. In mine the project was an RPG where the players would be involved in a continent-spanning fantasy conflict with fantasy races/magic/et cetera. So the worldbuilding priorities were to establish the fantasy races, magic systems, factions, geography, and other such things to give the ones who would be engaging with the world the info needed to engage with it. This seems to be a military-centered sci-fi art project
I want to be cautious as I go further because I don't want to backseat GM here, but I'll try to be focused. I'd say right now it gives a good impression of the organizational level of the military that most of these characters seem to belong to. There's setup for the environments of their homelands and the setting which I think most of the art is depicted in (the ocean planet and military craft). The weapons and technology have begun to have some worldbuilding on them, but there's room for more of that.
Some exploration of the species' traits of the Empire in regards to the habitability may be needed, as there seems to be an emphasis on the habitability of planets for the Empire when it seems to be a collection of a multitude of different furry species. It raises some questions in my mind ("if furry universe where people have animal traits and military deploying to ocean planet why send snake person instead of fish person") though I can understand that may open a can o' worms ("can x furry race and y furry race make babbies").
The factions tab is probably the area most ripe for expansion. A deeper look at states/cultures/species/ethnicities within the Empire can perhaps give deeper meaning to the character-heavy art thus far. An exploration of allies that work alongside the characters or antagonists who work against the characters' interests may also add to it (I see this already with one of their latest pieces on the shark species). The art so far and webcomics are very character-heavy so worldbuilding that helps elevate the audience's understanding of those characters is what interests a lot of people I think. In military organizations in media an easy way to do that is with the organizations themselves, different ones having their different "lore" behind them. Marines often get this a lot being the "first to fight" and "the few, the proud". Giving more history to these organizations or even smaller units can go a long way into telling us the motivations of these characters without the characters explicitly telling us themselves, we as the audience understand the prestige and prowess of the organization so we then understand a bit more about the characters.
Overall I don't think there's anything like… "wrong" so far. It's just a bit dense in some places to read and could use more focus on the characters since that seems to be the objective of the art. I also really like Helena's design so tell your friend to make more of her.
