This is just a version that I intentionally styled, but by default it's just a regular old QR code. Here's some examples, the top left is the default:

Checkout the demo site: bitcoin-qr.blu.cx. You can play with all the styling options and see the code there.

Also, if you prefer that the image be embedded in the QR rather than overlaying it, there's a boolean attribute you can set for that: image-embedded