I'm seeing the current Josh Keyes exhibit at David B. Smith Gallery again today. If you haven't seen it yet - it's only up for a few more days (closing on the 3rd). It's a really exceptional show and will easily top my favorite exhibitions of the summer and probably the year. I've mentioned Keyes several times before after first encountering his work at the Limited Addiction group show in March of 2007.
In the current show, I recognized the subject matter source Keyes used on his painting called, "Entangle I" from our many trips to Moab, Utah. The graffiti on the side of the monument is clearly borrowed from these petroglyphs by the Delicate Arch in Arches National Park: