What the heck is this thing and where can I find it in the scene file?
I downloaded Robin Marin's Cycles Material Test Scene ( http://www.blenderdiplom.com/en/downloads/584-download-cycles-material-test-scene.html ) because it seemed like a good one to try out the new Principled Shader. I noticed this in the reflection, and wanted to get a closer look, but I couldn't find it -- there's no background image and it shows up with render visibility on everything but the reflecting icosphere I put in turned off.
It's driving me nuttier than usual -- help?