As perhaps a few will know i put up heads up for nose art. Most do have a link to the name givers personal life. Girlfriend name, mothers name, cartoon names you name it.
I wondered if, i was in that situation and was allowed to name a plane what i would have named it. Given the fact one could have died in it.
There is no limit. No airplane no country.
Seriously though, I'd have to name mine "Always & Forever." It was my late wife's and my "salutation;" how we signed all our holiday cards,birthday cards, and notes to each other.