I think that nowadays, mainly with celebrity influences, people are more accustomed to "out there names". I've known a few people throughout different paths in my life who went by Fox, but not necessarily as their legal first name.
I think that if you love it, and can bring up your child to be proud of a name that may not be so common, then it's ultimately down to you.
I'm struggling to find a boy's name I love. I don't want one that's terribly common (I'm Emma and my partner is a James so we're always used to having like 456 children in our year with the same name!) but at the same time, I don't want a name that's going to put him in the centre of attention and make him self conscious - especially if he wanted to go through a serious career path in his adult life. (I'm mean, could you imagine having a police officer or doctor show up in your hour of need with a name like Buddy Bear?! What.)
That being said, I don't think Fox is that ridiculous. Now Badger on the other hand....