A couple I have used for fanfic ships:
All the great things are simple, and many can be expressed in a single word: freedom, justice, honour, duty, mercy, hope.
- Winston Churchill
Let not the deep swallow me up.
- RNLI motto (which I use for the Border Service cutter Silverfin
When thinking of plaque quotes, my first stop is pretty much always Winston Churchill, he has so many good ones that can fit just about any ship.