I recently have had the opportunity to try out a new book of advanced Christmas solos for piano by Amy B. Hansen, a friend and accomplished pianist/composer who shared some great insights with us about composing a couple of years ago, and I am loving it! Carol Encores is a great collection of Christmas carols that are definitely more advanced than many collections out there. These arrangements will really give your students something to work on. They are a fresh and original collection of well-loved and classic carols that will really add a flourish to a Christmas recital.
I think this is a book that both you and your more advanced students will really enjoy this Christmas season. Carol Encores can be purchased here.
Here's a fun music video featuring some of Amy's music - it gives you a great preview of her style used in her Christmas music.