I've got a Maltese and if she were younger, I'd get a Yorkie. Next time I plan on getting one of each.
Of course, Maltese are so wonderful, you can't go wrong with another one.
You'll learn a lot here about Yorkies (which is why I joined
) so hopefully you'll find out if the breed is right for you. I have a number of friends who have Yorkies and there is a big difference in personalities. Yorkies are terriers and feistier and actually were bred to do something. Maltese were never bred to hold down a job and would spend their life on your lap. I know many people who have both have described them as much needier than Yorkies.
I am usually in favor of adopting adult dogs, but at eleven months, your baby is the perfect age to add another puppy.
I think either a Yorkie or Maltese puppy would be fun. I wouldn't get a designer mutt, though. I don't believe in supporting that whole industry.