My favourite naming stories are ones that honour someone important to the couple. I love the sentimentality. It's also a huge honour to have your name passed down, especially when it's about character traits that the mom and dad hope to see in their child.
I think it would be especially meaningful if Kate and Prince William named their baby for his mother. Lady Diana had a profound influence on both William and his brother, along with so many others.
Here are some ways that they could honour Diana's memory.