iDealsChina publishes information and renderings of what it claims to be an "iPhone nano" case. Because silicone cases are skin tight it is a good way to judge what the new Nano iPhone is going to look like.
According to IdealsChina “It is the same height as the just release Nano but wider and thicker and with the same iPhone 3G contours. It has 3 sensors, camera, mirror screen but no 3G. Production will start on the 20th with 60,000 to 80,000/day pieces coming off the assembly line. Steve Jobs will be announcing it during the January MacWorld Show and you will find it in the stores shortly afterwards.”