The only images I could find of the setup were in a Singapore airlines video. Here are two still images from the video of the thumb keyboard and the USB socket on the seat back. There is also a larger keyboard in the video which appears to be plugged into the USB socket.
The eX2-branded upgrade of the Krisworld in-flight entertainment (IFE)
system running on Panasonic Avionics’ S3000i platform will provide 100 movies,
more than 150 TV programmes, 700 audio CDs, and 22 audio programmes – all on
Passengers will be able to access files on thumbdrives via the IFE by
plugging the drives into at-seat USB ports and using the ‘QWERTY-thumboard’
provided to run documents, spreadsheets and presentations on a system based on
Sun Microsystem’s StarOffice.
Airlines unveils A380 and lays out service plans, By Kieran Daly, Flight,