Variations on a theme

I am a huge fan of theme parties. Give me a pirate eye-patch or some eighties oversized t-shirts with those cincher clip things at the hip. Love it. Sign me up. Theme parties = guaranteed fun times.
So I'm struggling a bit with a 'theme' for our wedding, or whether a theme is really needed at all. What do you think? Have you been to a wedding with a subtle or not-so-subtle theme?
Before you start thinking I've lost my mind, let me explain. I'm not talking about a Victorian princess wedding with huge bustles and powdered wigs or anything--just something that Martha might approve of, like an apple-themed wedding in a rustic apple orchard in Washington. Or, a sweet nautical-themed wedding in Nantucket. Or similar.
The main reason I am hoping to come up with a somewhat subtle theme is that I think it could add a very personalized, meaningful touch to the day. And it would be a way to unify all of the hundreds of moving parts which are all starting to seem somewhat muddled in a huge tornado of blue, green and tulle. I want to have a clear, unified look for the day so that the pictures will all look like they came from the same wedding. But not too matchy matchy.
So far, the only visual that the guests have seen is the save the date (btw, which looks really super cute on my friends' refrigerators!). I might be able to use the flowers and leaves from the save the dates on the other stationery (programs, table cards, etc). Plus, the DIY invitations are coming together really nicely (more on that later) and my mom is hand painting blue hydrangeas (my fave flower) on every invitation! I love the blue/green flowers--so pretty. We had also thought about incorporating some fish somewhere (maybe on the table numbers, to tie in A's love of anything fishing-related) but I'm wondering if the look will be too visually scattered, with hydrangeas, fish, plus the H crest (!).
I am probably worrying too much about this, but I want everything to look great. Should we drop the fish idea and stick with the florals?