WE just recently took apart a fishing type room....hmmmm too bad I had a garage sale I would have glady sent you the stuff.
I took a fishing net and drapped it on the wall, all sort of mishapen. I used push pins to attach it too the wall. pull it up over itself in a few small spots and tuck in little wooden fish. Then I placed large bobbers, corks from old nets, a sign that said Gone fishin" and a metal anchor thing all on top of the net, sort of all around, no real order (which of course was well planned anyway, I am so goofy that way). This covered a nice size wall above or tv. I found the net at a local nautical store, but I bet they carry them at some of the local craft stores. Ours was big 4x6 at least. Oh and recently I saw someone had those glass balls that the fisherman place on their nets as floats...well remakes of them. If I think of where I will let you know. They are really cool. Oh and this net was the brown looking stuff, not the white, that wouldnt be as rustic
Also did this...cut a small piece off the end of the net and drapped it over the metal bottom of our lamp, you could attach some of this to your brown paper lamp shade, using fishing line as thread so it doesnt show.
Or you could cut a piece to use as your table runner....

and add a couple rustic candles in a old metal dish on top with some stones around the candle on the dish...through a wooden bobber or two in the dish also, just for the fishin' effect.
Check out your local craft stores or boutiques for one of those neat little wooden canoes made out of bark to sit on the tv or a end table, if its small enough it can be a candy dish...
Make a blanket out of the fleece that matches your room with fishin or nautical stuff on it.
Oh and one of the cheapest ways I found to bring in the theme is to go to a discount wall paper store and look for a border that matches the idea I want and put it up. It changes the look very quickly and if you just install it using the prepasted method on the back it can be removed easily in the future. For your room you can even use a nautical map theme border.
Hmmmmm lets see what else did we do....oh let me go look at my sons roomits nautical...oh...we place little 4 x 4 inches ships wheels that are supposed to hung on a peg..on top of his valances, just used a pin and pinned them by the little ropes to the front of the valance right at the rod height. This was easier then getting new curtains.
Found a shelf at a local craft store and placed a few nautical things on it, you could put up any shelf and add pics of trips to the lake, a little metal lantern, etc. Do you have a Pat Catans near you....they had lots of nautical things last time I was in.
Am I making you crazy yet....here is what my sis in law did for her nautical room...she bought a grapevine wreath, wrapped in a plaid ribbon and added little nautical things she found a the store, made a bow and again added rustic things in the bow. very cute!! She even found a sign that said fish stories told here to it.
Well hope some of these ideas help you out.
have fun!!