There is a script he included to change the characters
CHANGE THE VIDEO/IMAGE
Herman has supplied an awesome video changer script, which you run on your PC which connects to the Pi and changes the image and picture and reboots it, for this to work you will need to have your Pi plugged into your network , via LAN cable , OR, if your an advanced user you can SSH in and set up your wireless network as per instructions HERE – Remember unlike a PC a Pi will need to be rebooted to actually connect to the network, even if you plug a cable in.
Open up the folder named “SCRIPTS” on your PC, double click one of the many options such as Gent-4 and a script will automatically open and show some text on the screen (hopefully with no errors) which will tell the pi what to show and then it reboots the pi
you can then unplug from your network (if you need to!)