Jack - I would use John or Jacob, and nn him Jack. Jack is v v popular.
Nash - no. Mash, Rash, etc. and in any case it's a surname not a first name.
Obie - no. Star Wars.
Ocean - no. Oceane is a popular girls' name in France, and I can see why, Ocean has a v feminine ring to it.
Bella - I would use Isabel/la, Arabel/la or Annabel/le and nn her Bella. But I probably wouldn't use; this name is used in Twilight and will be massively popular in the next few years.
Lucy - One of my favourites of all time.
Tilly - I would use Matilda and nn her Tilly. (Though tbh I'm not hugely keen on either of the names - personal taste and nothing more)