Another problem with my art idea was that I wanted the children to be surprised by the end result. This meant not being able to tell them very much about why they were doing this cutting and pasting, and why everything was supposed to be the same color. So they lost interest fairly quickly. In hindsight, this seems a fairly obvious flaw in my plan!
And the final problem was that I found I was too invested in how I wanted this project to turn out. It wasn't primarily about the process - the final product was also extremely important to me. So I was really unable to let the children work on it freely. In the end, I did most of the work on this project myself. I did have a little help from one of the children (and another adult) on Thanksgiving Day, and three other adults gave me a little help on a couple of Sundays. But the bulk of it was me.
By the second Sunday of Advent (our first Junior Church session in Advent), I was able to place this in the room: