It's an interesting question. My initial thought is to say that, assuming cryonics works to preserve the same thoughts and personality upon revival (and that's a really big assumption, science hasn't found a way yet [as far as we know]), then I would say it essentially counts was a way to extend your life. It's not immortality, not really, because you're still vulnerable to accidents, the device breaking down, other people purposefully shutting off or destroying it. And whatever device you're using will have a finite source of energy.
So, the real question is, is it wrong to use medicine and technology to extend your life? No, fundamentally, I don't think so. I mean, is it wrong to try to extend your life by using scientific discoveries in nutrition and exercise to guide your food and exercise choices? Is it wrong to use a kidney dialysis machine if your kidneys fail? I think if you're going to categorically say that using cryonics to sustain your life is evil, some kind of abomination, it raises questions about all other kinds of life-sustaining medical care.
And, from a Christian theological perspective, I don't think it really changes anything. Jesus will return one day to judge the living and the dead, including you, whether or not you're in some kind of cryonic stasis.