Open file /etc/issue and change the text:
# vi /etc/issue
You can use this to add some new info or ASCII image.
The images can be transformed into an ascii image by using convert image to ASCII.
One example to convert a picture into ASCII TEXT, HTML is this website: picascii.com
The main problem can be if you have escape codes consist of a backslash (\) immediately followed by one of the letters explained below:
\b : Insert the baud rate of the current line.
\d : Insert the current date.
\s : Insert the system name, the name of the operating system.
\l : Insert the name of the current tty line.
\m : Insert the architecture identifier of the machine, eg. i486
\n : Insert the node name of the machine, also known as the hostname.
\o : Insert the domain-name of the machine.
\r : Insert the release number of the OS, eg. 1.1.9.
\t : Insert the current time.
\u : Insert the number of current users logged in.
\U : Insert the string “1 user” or “ users” where is the number of current users logged in.
\v : Insert the version of the OS, eg. the build-date, etc.