It is worth noting that thoughts on "spirituality" should not be limited to Christian spirituality - or even "religion" for that matter. When thinking about the spiritual aspect of all visual art (and at this point I'm in favor of arguing that there is one) my interest is in the idea that artists are attempting to navigate a balance between what is visible and invisible - between what can be described verbally and what simply must be experienced.
Having grown up in the Bible Belt, my experience with the spiritual is slanted heavily toward the Christian. For this reason I have taken an interest in the creative life of Clive Staples (Jack) Lewis. Not that Bible Belt-ers would be quick to embrace the creative work of a man known for his love of tobacco and beer. Lewis seemed to have little trouble maintaining a balance between what he could prove to be logically true and what he could not prove but felt must be true.
My interest at this point is that that Lewis was able to use his creative works to make people of all backgrounds and religions think and ask questions about life. There were no sermons or cheesy "After School Special" moments. He posed questions and where there were blanks, he simply left them blank.
When he wanted to help the war effort in England during WWII it is important (and related) to note that Lewis refused to use his writing talents to create propaganda for his country.