That's so great...tomorrow...you must be nearly insane with excitement! Congratulations!
Why do you want to change his name...just curious...Max is a really cute name for a little guy like a Yorkie...
My boy, Brody, whom I didn't rename when I got him as an adult last year, has a hoodie that reads, "Mommy's Tough Guy"...and it fits him to a "T" !
If you decided that it fit and and you didn't change his name, you could say "Max" is short for "Max-A-Million"...lol...cuz this boy is gonna give you a million smiles, a million kisses, a million belly laughs, a million...well, a million everything-goods!
Seriously, though, I knew people with a huge Belgian Shepherd who's name was as long as my arm but included "Maximillian"...and no, I have no idea how it was spelled...and they called him "Max" for short. He had lost substantial weight due to heartworm treatments when I met Max and his weight was "down" to 120 lbs. I think some of the new micro-compact cars are bigger than Max, the sweetie, was. So, any time I see a bitty dog named Max I automatically think of the Max who used to tear up the street to get a hunk of road asphalt as a chew toy!
I am sure you will choose a name that fits your new baby. Can hardly wait to see his pix...