I honestly think this is a terrible idea. Well, more specifically a terrible idea on a gun that might ever be used for self-defense.
I know some people are likely to disagree with me on this and it's a heavily debated thing.
I love customization, I'm all about it, but known gun lawyers who have litigated real life cases have specifically noted over and over that cosmetic things like skulls and such on a gun used in self defense make their job harder, plain and simple. I'm talking very specifically of novelty cosmetic things, not mechanical improvements.
Of course if it's on a purely range gun or safe queen, then sure, go nuts and have at it. Don't be putting skulls on your carry gun though.