QRImage is a web app to generate QR codes with images.
Bit size:
Larger sizes hide more of the image, but are easier to
scan. I found that a size of 30 works well.
Error Correction:
Higher level of error correction makes bigger qr codes, but
also allows you to hide more of the QR code. The former is
more relevant to this app.
Border Size:
Size of white border around QR code. Typically need some
border around the code, but depending on your use case you
can get rid of it.
*Note that these QR codes may not work with every QR code
reader, so be sure to test them first. If you are having
trouble getting them to read, you may want to increase the
bit size.