My sponsor is a devout Christian and I was firmly agnostic when I got sober. Over the years, I've developed into something of an accidental Buddhist -- not a religious label at all but more of a philosophical one. Like Steve, I've found a lot of inspiration and guidance in the religion of my sponsor and it's helped me to sponsor others who are Christian, Muslim and agnostic like I was.
So long as your sponsor has a firm understanding and respect for "God as [we each] understand God," then I don't think it matters. If, on the other hand, your sponsor is insisting you adopt his understanding of God, then maybe you should search for a new one.
Peace & Love,
Sugah