Any and all text.
As long as a product has a personalisation box, you can customise it. There are no robots here. The very real human (Hi, I'm Tavie) who reads it can discern between a name, an address, and a design note.
Fancy a book stamp design for an address stamp? No problem! Let me know. Want to use an address label for your wedding favours? Sweet! I got you, fam.