It looks like the special effects team actually read the source material: most of the alien members of the Green Lantern Corps look pretty accurately represented, especially Hal's nearest neighbor, Tomar Re of Space Sector 2815. (We, of course, live in Space Sector 2814.) Tomar Re looks just like he did in Gil Kane's original design, a fin-headed alien fish/bird hybrid. Likewise ultimately-evil Sinestro, GL drill sergeant Kilowog, etc., etc.
If you don't read the comics, you will have no idea what I'm talking about. If you came to this blog because you know what the title means, I'm preaching to the proverbial choir.
I want to recommend that you read Green Lantern: Rebirth by Geoff Johns and Ethan Van Sciver. It's available in trade paperback form, and I understand you can even borrow it from many libraries. It's well worth it, even if you've never read a comic book before in your life.
And yes, I refuse to use the pretentious convention of calling it a "graphic novel" or "sequential art." It is both of those things, but never mind. At the end of the day, it's a comic book.
And a great one.
By the end of it, even if you can't tell Batman from Superman, you will understand who Green Lantern is, what he represents, and in what kind of universe he lives. And if you do have some passing familiarity with the character of Green Lantern, you will be delighted by all of the care that went into crafting this story. I grew up reading about Hal Jordan, the fearless test pilot who was chosen by a dying alien to take over the ring and the green glowing battery that charges it with the power to create anything he can imagine -- for 24 hours. It had all the elements an 8-year-old kid could want -- aliens, crooks, black and white morality, and lots and lots of action. It was written largely by unsung writers Gardner Fox and Bill Finger, but sci-fi greats such as Alfred Bester and Edmond Hamilton all had turns with the character. Then in the eighties and nineties, things soured. The powers that be at DC comics decided to shake things up and replace the old heroes with new guys in their masks. They made Hal a villain, gave the ring to a new kid named Kyle Rayner, and a lot of us stopped reading.
Green Lantern: Rebirth gives us back Hal. It recaps his history, explains and excuses his turn to the dark side, and even explains the dumbest conventions from the 1960's stories (things like the fact that Hal's ring wouldn't work on anything colored yellow. I know.) Rebirth features most of the great heroes of the DC Universe -- Superman, Batman, Wonder Woman -- and puts Green Lantern right up there with them. If you give it a look before the movie comes out later this spring, I think it will add a lot to your appreciation of the movie. Even if it's a turkey, which I hope will not turn out to be the case.