There appears to be a total of three title screen backgrounds.
The default title screen looks like this:
achieve ending [B] (complete the game as 9S),
then you will unlock this title screen:
However, once you achieve ending [E]
and choose to delete all save data,
your title screen will change to this one:
From what I have found online, you cannot manually change them and, going down the list, each title screen appears to replace any previous one, which means unlocking the final one will make that your title screen permanently from that point forward.