The Church would not have a specific position on the current "zombie" fad because it doesn't need one. It has already spoken on this subject in other teachings.
For instance, according to Websters, a zombie is a creature that has been reanimated after dying by a supernatural power according to voodoo beliefs. Voodoo, as we know, is a religion that is derived from African polytheism and ancestor worship and employs various forms of sorcery.
The Church does not believe in reanimation after death or in any other voodoo belief for that matter. On these subjects, we have plenty of Church teaching.
First, we do not believe in the reanimation of the dead. The Catechism makes it very clear that man dies only once at which time he is judged by God and deemed worthy of heaven, hell or purgatory. (No. 1013)
As for voodoo and sorcery, the Church has also spoken quite bluntly. "All practices of magic or sorcery, by which one attempts to tame occult powers, so as to place them at one's service and have a supernatural power over others - even if this were for the sake of restoring their health - are gravely contrary to the virtue of religion" (No. 2117).
Hence, it follows that belief in zombies is antithetical to Church teaching.
However, people who dress up like zombies might not be doing so because they believe in zombies. They could just be caving into the current "Walking Dead" craze and not really meaning to celebrate the occult beliefs that these costumes represent.
But that doesn't mean dressing up like a zombie is a good idea, even in fun. In fact, bishops in the UK have gone on-the-record asking parents to stop dressing their children in Halloween costumes that celebrate witches and the occult.
Obviously, the same advice could be applied to dressing up like zombies for a wedding.