As a preface, no, Mr. Wong isn't in prison for the rest of his life because he had a Punisher skull on the grips of his gun. He's in prison for the rest of his life because murdered a family over a domestic dispute.
Still, I gotta say, having a Punisher skull on your gun probably isn't gonna fly well with a jury.
We already have research that people are more likely to want to ban guns that are all black as opposed to guns with wood furniture regardless of function. Putting extra paraphernalia on your gun isn't gonna help you in court.
Similarly, in the Daniel Shaver case, the cop who murdered him got off. The fact that the cop had, "Fuck You" written on the gun that he used to murder Shaver was a factor that I took note of in researching the story. Apparently the judge didn't allow that fact to be presented as evidence. Still, you never know what a judge is going to do.
I'm as in favor of people having guns for self-defense as anybody. I also love guns that look cool. I'm a visual person. The reason I don't like Glocks isn't because they don't function well -- they do. They're just not attractive
Still, the point remains, it's probably a better idea to not put a skull on your gun, or to write "Fuck You" on your gun, or basically put anything on your gun that'll give a jury reason to believe that you were looking for trouble.