Since Apple has already released technical drawings of the 3G iPhone to accessory manufacturers, renders such as this EXO Mask case have surfaced. From the images, it looks "a bit thicker, with a more pronounced curve to the back." Click here for one more picture.
You'll note the larger, more curvy back, space opened up near the earpiece for the rumored front-facing camera, and what appears to be a non-recessed headphone jack.[via Gizmodo - Engadget]