Just created my new sig using Google’s QR code API ( http://createqrcode.appspot.com/ ).  It creates the codes with error correction (there are some settings that you can use to modify this), so its possible to actually delete a part of it and enter your own image/text in the middle of the QR code.

I had to play around a little with my name in the middle.  If it is not aligned properly on the QR code or if it covers the wrong area, the code won’t be recognized.