If the wall in the previous post looks like a mural to you, here's another "maybe" with fewer tiles and more wall. (I didn't count the tiles. This one just seems more sparse to me.)
This act of devotion in front of 505 S. Columbus was finished just a month or two ago. Here's a close-up from the north end:
Update (May 2, 2013): There's a close-up of the mailbox in the distance (at the near end of that far wall) in today's post on the Tucson Mailbox Art blog.