Anything is possible when we take it one step at a time. Any task, any goal, no matter how large, can be accomplished in small increments. The same is true for large paintings or murals when we work one square foot at a time.
Painting in squares gives us a solid foundation to work with, focusing only on the square in front of you. When the squares are all put together the underlying image shows through. The individual participants' work can still be seen along with the contribution to the whole.
Below are other examples of paintings and murals - by the square or square foot.