One of the ideas with traditional christian icons is that they are actually a portal to the divine. The painting is some how embedded with the actual power of God and this can impact the viewer in a life changing way. There have been miracle associated with particular works of art.It was a firm belief in the middle ages that coming before a painting would connect one to the healing power of God and they would be made well. I remember a friend recounting coming across a van Gogh painting at the Art Institute of Chicago and immediately being brought to tears. Tears are often the evidence of a healing some where deep in our heart.
Art making is a process of making the invisible visible. It is what Jesus accomplished in coming to earth. He said "Anyone who looks at me sees the one who sent me" (John 13:45)
I know a piece of art is often thought of simply in terms of decoration and it certainly can be that but it also can be so much, much more.