The USB Updater image is officially headless, meaning it's not designed to make any use of a display, whether external or internal.  Recently one downstream developer created a novel modification to this paradigm and suggested we should share it with the community:

Using openvt, you can add text output to the LCD panel on the TPC product.  This would be added to the script thus:

openvt -c 1

This will allow stdout and stderr to be output to the LCD screen.

Going one step further, it is a good idea to disable the Linux automatic backlight-off feature thus:

echo -ne '\033[9;0]' > /dev/tty1

If turning off the backlight is desireable (for example in a battery-operated environment), changing the 0 in [9;0] to some other number will enable the screen-saver function, disabling the backlight after the number of seconds specified.