she already has and she is called renesmee carlie cullen ( the name is combination of the names of bella's mother and father (renee and charlie) and edward's mother and father (esmee and carlisle))
I think it would have been interesting if she would have named it Elizabeth, after Edwards mother...or atleast name her Carlie Renesmee Cullen, it has a better ring to it, buut then no one could have called her "Nesse" and she wouldnt have attacked Jacob when he called her "Nesse" because Nesse reminds her of the loch ness monster hahahahhahaha (one of my fav. parts of Breaking Dawn =)...)
Bella was thining about calling the baby Ej because she thought he was a boy. When it turned out to be a girl it was named Renesmee Carlie Cullen Renesmee is a mixture oF Two names put together to make 1 which are Renee ( bella's mum ) and Esme ( edwards mum ) Carlie is another mixture of Carlisle( Edward's Dad) and Charlie ( Bella's dad) to make the middle name. and Cullen is obviously just edward and now bella's ( because they are married ) last name.