I'm thinking that it has to be 80X80 something. I'm assuming that's pixels.
The smallest pic I have is 12.4kb and 320x240 in my Vista picture gallery and even if I crop it, it won't be THAT small. I'm graphically challenged and only have the most basic of image manipulation stuff.
I really want to start using my name and pic in case I ever want to 'brand' something, but I honestly don't know how to upload my picture...