Here is an Advent calendar shaped like a Christmas tree. Feel free to download the template here or click on the drawing itself. I like to take a copy of the 8 1/2 x 11 page to a commercial copier, enlarge it to 11 x 17 inches (about 129%), and print it on white card stock.
This calendar is designed to start tomorrow November 27, the first Sunday of Advent, and go through December 24. You can add dates to the shapes and start drawing in any of the twenty-eight shapes–one a day. The star at the top of the tree is not considered a day unless you want to make it Christmas.
Last Advent, I did a Praying in Color workshop at a Catholic parish in Pittsford, New York called St. Louis Church. The woman in charge of organizing the workshop gave each family a piece of string, tiny manila envelopes and clothespins to create an Advent calendar. Each day someone would draw a prayer on an envelope and hang it on the clothesline. Families had different ideas about what to put in the envelopes–candy, toys, little notes….One idea I liked: Each day anyone could put pennies, nickels, dimes and quarters in the envelopes. At the end of Advent the family would decide where to donate the collected money.
Depending on how much space you have, the clothesline and the envelopes can be small or large.