Is the wireless power back channel communication option capable of doing high speed transfer for mobile device firmware updates or picture transfer? 

No, the communication that occurs from Rx to Tx (part of the WPC communication standard) or Tx to Rx (IDT’s back-channel communication) is not meant as a high bandwidth communication channel.  It uses the energy transfer band to facilitate this communication and may be used for two-way authentication or passing of lower bandwidth information, but it’s not meant as a substitute for NFC, wi-fi, or Bluetooth.