There are some photos from zoogue, and clamed these are iPad nano images we still can tell their source is true or not, any way let's have a good look at there iPad nano pictures:

Instead of a thirty-pin dock connector, the “iPad Nano” takes on a variant pictured only once elsewhere. The size difference between the thirty-pin and this new mysterious port is substantial, possibly suggesting a switch to microUSB by Apple amidst pushes for regulations that implement a universal charging solution for mobile technologies.

via zoogue