In the days of DOS, you used to be able to manipulate the screen output by loading up the ANSI.SYS driver and using ESCape sequences or by creating your text/images using an app like thedraw.
Checking for a modern solution for ANSI.SYS I came across ANSICON. With this app/utility installed, putting ANSI escape sequences in your txt file may work - I can't try it at the moment as I only have a Linux laptop at my disposal so feedback would be useful!
Edit: Thinking about things, I don't believe this will make centring text any easier as I cannot find an ANSI sequence that defines 'centre text' on a display - only for a printer - but this may be of use for designing screens so I will leave the answer here as it is.