[Note: The following series of comments were inspired by the "Interactions" image released by Perpetual which showed a starship in an asteroid field near a planet, communicating with an alien shown in an inset "viewscreen" graphic. Although things are likely to change as another developer takes over production, the discussion about the pieces of that image spoke broadly enough about general issues related to the visual style of a Star Trek MMORPG that I thought it might be worthwhile to preserve the conversation.]
Bearing in mind how early in production Star Trek Online still is, while the semi-realistic graphics for the planet, asteroids, and ship were fine, the artwork used for the "Overseer" alien in the viewscreen snaps me right out of immersion in the gameworld, just like the similar cartoonish headshots used in System Shock 2 did. All I can hear in my head is "it's a game! a game!"
Can the cartoonishness of images of people be overlooked? Sure, as long as immersiveness is promoted sufficiently in other ways. But why should people-images be an exception to visual elements that contribute to immersion?
I don't mind Star Trek Online being a game. After all, that's what it is. But as I've suggested, I think it's also fair to point out that some (many?) gamers will want it to feel like a world, too, and in particular a world in which the beings with whom we'll interact as Starfleet officers present plausibly believable situations. Achieving that goal gets a lot harder if the artwork of other beings moves radically away from the semi-realism of the TV shows and into fantasyland World of Warcraft territory.
This is not a criticism of the artist. The work here is excellent, even more so if we're talking about an animated image. But, as with System Shock 2, I have to question the decision to go with this approach. (For what it's worth, Jonathan Chey of Irrational later acknowledged in a Gamasutra postmortem of System Shock 2 that the cartoonish character portraits would have been improved if time had permitted.)