Website Indie Revolver has shots of what may be a version of Imperial stormtrooper we'll be seeing in Episode VII. And the photos are very convincing.
Spoilers of a sort ahead. But mostly speculation.
Here's the first design revealed by Indie Revolver:
Comic Book Movie says that this is being referred to as a "Jungle Trooper" because it's being featured in filming at the tree house set at Pinewood Studios.
For my part, I agree with Indie Revolver's take that it appears closer to the Snowtroopers that appeared on Hoth in The Empire Strikes Back, what with the sleeker, flared helmet. With a bit of the Imperial Guard's eyepiece added on. It seems more natural for a "Jungle Trooper" design to build on the Scout Troopers seen on Endor in Return of the Jedi, which this definitely isn't.
From left to right: Scout Trooper, Snow Trooper, Imperial Guard
The second helmet looks like a continuation of the original, much like the starship J.J. Abrams revealed in the Force For Change video felt like a continuation of the X-Wing. If nothing else, the influence of Ralph McQuarrie is strong in the new films.
The second helmet has some changes: it's asymmetrical with only one vent at the bottom left, the "mouth" is a black mesh (better seen in the close up photo), and the two black "eyes" are completely connected by a black visor piece.
UPDATE: Indie Revolver has posted a photograph (i.e. not concept art) of a physical version of the second helmet, which we've included below. The photo was originally posted at the RPF, "a site dedicated to replicas of movie props and costumes." It appears to confirm the unilateral placement of the vent mentioned above. No clear indication yet whether this is an actual movie prop, or a piece of concept art realized by a costume company, but we'll keep you updated as we learn more.