My plates are personalized, but have nothing to do with the XF. They have a personal meaning.
But if someone is looking for suggestions, most of the more popular ones are taken. Here are some suggestions hat may help, or trigger some ideas:

USA BENZ,
X FUEGO (fire in Spanish)
My Cross (??? well?)
NO XF 4 U (for those who are allowed numeric/alpha mix)
LUV MY XF
FAST XF
XF Zooms
XF RDSTR
Roadster
DA RDSTR (for Chicagoans)