This wooden church Advent calendar is on sale at Target for $6.99. I think with a few touches, it could be turned into something quite inspiring and a family treasure for generations.
Painting the roof a more roof like color with shingles or tiles approximated in permanent ink, and the ground rendered a more realistic color would help a lot, as would moving the small cross to the top of the steeple. Painting the door brown or another dark color would add some visual weight as would using the eyes from a large hook and eye set as faux iron work. Those handy with Photoshop could add stained glass (printed on labels for easy fixation).
Inside each door, one could place a verse from the readings of the day and other small treasures.