It would be a great new feature, if it would be possible to include a QR Code with the guest account password into the ticket page. This would make it easy for the user to copy a complex password into the password field of the captive portal.
For Android devices its also possible to include more informations like SSID name and encryption (for WPA2-PSK protected SSIDs) and the pre-shared key into the code, but not every device could use this informations. Some iPhone apps could also collect this informations from the code, but the guests passwords would be the most usefull information and is useable with every QR code app.