I love green, I got a bit sick of blue after DS1 had a blue nursery and I've been actively avoiding it ever since. DS1 has a dinosaur themed room but what I did was buy "plain" things from Next, so he has blue curtains (I now realise I said I was avoiding it but it's a dark blue lol) with a lovely green, red and blue rug and then he has ikea expedit shelving with coloured boxes, then he has dinosaur bedding and wall stickers. I figured it would be easy to mix it up of he got fed up of dinosaurs of if/when the boys share (we can't decorate).
Then DS2 has a neutral nursery set from Next which is cartoon woodland characters, beautiful colours lots of orange and a kind of bold but baby green, the characters are owls, birds and hedgehogs.
Edit: just seen you've found a theme, that's lovely I really like that, we're not allowed boats with DH being RAF, I wasn't even allowed to get a sailor suit for DS2's christening