A frame from the upcoming CG television ad for Halo 3, due to be broadcast the evening of December 4.

Accompanying an article at 1Up about Halo 3's multiplayer features, this image was confirmed by Bungie's multiplayer lead, Tyson "Ferrex" Green, as concept art of the Spartan Laser, which is projected to be an anti-vehicle weapon.

http://carnage.bungie.org/haloforum/halo.forum.pl?read=757593

From the Bungie Update:

"over a period of several months and literally hundreds of files, we have the final Halo 3 logo. We hope you like it and if everything goes according to plan, you’ll see a LOT more of this in the months ahead!

Looks like the color and texture of metal on the underside of the Halo rings; although at a distance, the colors also look like an Earth-like world seen from a distance, the mix of blue, green, and white.

Robert McLees said this image is worth a thousand words about the Covenant-Flood relationship.

This image from the documentary describing the process of creating the Halo 3 Announcement Trailer sparked much speculation: are these familiar species in new costumes, or entirely new species? The former seems more likely but some fans cling to the latter.

Official Bungie screenshot, from the same version of the game used to make the Halo 3 trailer, but not actually from the trailer. Released with the 2nd Weekly Update after Halo 3's announcement. Suitable as a desktop wallpaper.