Add terminal session with network to login in screen
Solution 1:
Create a file called terminal in /usr/share/xsessions with the following content:
[Desktop Entry]
Name=Terminal
Comment=This session logs you into Terminal
Exec=gnome-terminal
TryExec=gnome-terminal
Icon=
Type=Application
Solution 2:
If you mean launching only terminal with no desktop, I don't know how to add this to login screen, but you just could switch to the terminal by Ctrl-Alt-F1 to Ctrl-Alt-F6