Defiance is the one with Megatron kneeling before some object that looks similar to the poster face. Below are two additional covers for issue #1. Click here for the sneak peak.
As for the story, according to mini-series writer Chris Mowry on his blog:
The series takes place before the events of the first TRANSFORMERS movie. It expands on the events from the first movie and this summer's sequel. If all goes well, it'll help expand upon the movie universe and set the stage for future stories as well.I still haven't figured out how this series plays out compared to the other prequel mini-series Transformers: Alliance. My best guess is Defiance is more of an origin story for the entire movie universe while Alliance is a direct prequel for the upcoming sequel. The issue will be out this Wednesday, so be sure to check your local comic book store. Thanks to Gregory for the links and issue 4 cover and lowHertz for the issue 1 covers.
It's an origin that's a bit different. Cybertron isn't the same planet that we know. It's flourishing. Characters are working together and not killing one another. The society is based upon peace and the expansion of their knowledge. Megatron serves as the planet's protector. With his soldiers, the planet has enjoyed peace for a long time. Optimus heads up the science and construction division. He's the "blue collar" character who will eventually find himself thrust into a situation that he's never been in before. It's a different time and a very different place, but it all goes horribly wrong.