I do have it in the same location Benjamin gave -- and I don't have anything like shapeshifter -- but the BezelUI folder for some reason is not visible from Finder by default. So I had to terminal to the location and then "open ." But after this, I was able to see it.
It contains bezel images like the icons that flash when a bluetooth mouse or kb is acquired or lost, or when you adjust sound. For instance, on my iMac, there are only a few that don't work, and I don't think they're applicable -- such as the contrast one (not applicable to LCDs) and the Door Ajar one (not applicable to anything but a PM or MP). I think on the right mix of computers, almost everything in the folder gets used now....