It's called "cinema mode" in Linux? I think I'll be going with that. I was really leaning towards "padding" for a while, but I'm sure only web developers will be familiar with the concept.
Creating the effect in the program has allowed me to hide the title bar, menu bar, window borders, etc. I'm sure it will be more pleasing than what a secondary program could achieve. I hope it works with all versions of Windows and on Linux with Wine.
Other ideas I've tossed: Matte, Curtains, Black-out.