I don't have my books with me but I seem to recall in OotP that the Death Eaters wore masks but I also remember hoods in DH.
My specific question is whether there is any record of a Death Eater without a Dark Mark (e.g. Fenrir Greyback or Stan Shunpike) wearing a mask, hood or both. (I'm pretty sure Stan had a hood, but once again, I'm currently bookless.)
Also, if I'm right and masks were mentioned, is a description of them given?