What happens when you reach your 10 year mark? Do you get a loyalty box or anything?

As memory serves, there isn't anything special rewarded for ten years. You still get a Loyalty Box like you would on any other yearly account anniversary.

okay thanks

Nope... no special thing for the 10th year (though that would have been cool). My account is 11 years old and I only got the same loyalty box that was given out each year previous.