It's looks similar to icons I see temporarily in the lower left, and lower right of my screen. When I play games through STEAM, I'll get notifications in the lower left hand, telling em which games my friends are playing. But that icon is only visible for a few seconds. I also have FRAPS running, with the dispalyed FPS counter running in the lower right. Origin games has a pop up in the lower right, that works like STEAM regardig my friends playing such and such game. Although I can't recall if it's only visiable on the Desktop, or during full screen games.
Perhaps you have some utility/app/game service that is running and that is causing that icon to come on screen?