Forgive me if this seems to be going off on a tangential, I'll pull it back towards gaming on occasion, but this has been something that has been on my mind of late. Masks are powerful tools. As a society we generally seem to frown on them. We take them as a sign of weakness, as a sign of hiding who we are. The common assumption is that someone who wears a mask does not want to own whatever actions they have committed. This is certainly the truth in some cases, bank robbers for example wear masks so that they are harder to catch, but is that all there is to it?
More Than Just Hiding
So, I'll admit that there is the possibility that someone who is wearing a mask is hiding who they are. There is also definitely the fact that they have made themselves harder to identify, just in general. But that isn't always the case. Even in the real world there are several figures in pop culture who are more easily identified due to the masks they wear. The most popular right now is probably Lady GaGa. While she doesn't always wear a mask, she wears them enough that people have commented on them, and the masks - along with the rest of her get ups - are a big part of her identity as a performer. The other two big ones that stand out in my head right now are the bands Slipknot and Hollywood Undead.
While I can't speak for Hollywood Undead, or Slipknot at present, one of the original aspects of Slipknot wearing the masks was to hide who they were. It kept the focus off of any one member of the band, and put it on the entirety of the group as a whole. By hiding who they were, switching masks, and moving around the stage, they created a spectacle as a group. Presumably this has since changed, since their lead singer became famous on their own, but the idea is there. There is more to wearing a mask than just hiding who you are, even if that is - admittedly - a mask's primary function.
A Sense of Identity
This may seem strange after what I just said, but a mask can give a sense of identity. To find that out you don't have to look any further than DC Comics and Batman. The dual identities of Bruce Wayne (Him and Batman) is a common theme in the Batman comics. The mask doesn't just hide who Bruce Wayne is, it is Batman's face in its own way. Batman is a very different person than Bruce Wayne, and several stories - including the recent movies - have even posited that it is Bruce Wayne that is the mask for Batman, and not the other way around.
A Mask can give a sense of identity in other ways as well, and this is played up in several comic books (most of them wear masks, and some of those are very distinctive). You can also see this feature of masks in games like Legend of the Five Rings, specifically with the Scorpion clan. In the L5R universe, the Scorpion wear masks not to hide who they are, but to show what they are. Stay away, I am not someone to trust. I lie. I cheat. I steal. I will ruin your life. The mask says, playing into centuries of stories and plays - often written by the Scorpion themselves - to create an identity of what the Scorpion are supposed to be. All the while, the person under the mask says altogether different things.
In many ways a mask can give a better sense of identity than even a person's face can, at least in fiction. The more detailed the mask, the more identifiable it can be. This is added to the fact that masks, generally, are rare things to be worn. A distinctive mask calls out to be noticed, and that mask can give a sense of identity for the person where even flesh and blood may fail.
More Than A Person, An Idea
This is something else that comes up with masks a lot, and something you may really want to consider for future characters in your games. I touched on this with Slipknot, and then again with Batman, but a mask can transform something into more than just a man. A mask can be a symbol, a mantle that anyone can take up and ride along to new heights. For gamers, the most famous example is probably the Dread Pirate Roberts from Princess Bride. Roberts is a masked pirate, who dresses in all black. Roberts is said to be nigh uncatchable, and has been pirating for nearly 30 years. Only, Roberts is not Roberts, he is Wesley (look, the grace period for spoilers ended on that before most college students were born). Wesley isn't even the first inheritor. What is important is the name, and the mask, the rest is just someone else playing into an idea that has already been fostered.
For a more modern example of how this can work, watch Code Geass. In that, the main character uses a mask to not only hide his identity, but to give face to a revolution. A face that others can rally behind, and at a key part, a face everyone can take up for themselves to escape persecution (this doesn't actually spoil anything :) ).
There are a lot to masks, and a lot of ways to use masks. With Super Hero games being more popular than ever, and just with the extra level of "something" that a mask can add to any character, maybe you'll consider one with your next character? I know I am.