A couple options (totally different methods) to display big titles, e.g. a 'game over' screen or 'the end' in the style of silent movies.
You draw a few sprite tiles with corners and reusable portions to form your title.
Pros: all the advantages of Pico-8's maps and easy to edit your title
Cons: you need some free area in your Map and you spend tiles of your spritesheet
You can use this spritesheet to P8scii string converter here to obtain a printable string that will display the title (or logo etc..).
Pros: no map, no spritesheet, just a big string
Cons: pick your image carefully, avoid one with many stray pixels (read hints in the linked One-off page) or it will eat compressed characters space.