We were also in the same situation and really didn't expect a boy to appear so had only a couple listed that we weren't really fond on but thought there was no point putting much effort into them thinking we would have a girl!
I liked names that were not common but not unusual you think wtf were u thinking! Strong and can't be shortened was my criteria!
Middle name was also going to be William if a boy haha!
Surprisingly enough a little boy joined us in May this year and we named him Axle William, his 4 yr old sister is Mollie Marie.
Hope that helps! It took us 4 days to name him!!!