You limit the power of God if you say that pets are not in heaven.
Well said! To say, "Well, it's not mentioned in the Bible.", could just mean that people back then didn't have 'pets' like we do today. There were farm animals and such, but I think we have far more of a relationship - so to speak - with animals as loved, precious members of our family now. God cared enough for even the smallest sparrow to find something to eat, I find it hard to believe he doesn't stay consistent in that care.