I'm in the process of switching my son's room to a Nautical theme. Here's a cover I made for a throw pillow to go on his bed.
I like to make the envelope style of covers so that I can change them out when my decorating mood changes. I've been using this tutorial for a few years.
I did do a few things to add detail:
* I added piping around the edges - sewn onto the pillow front, then clipped the corners of the piping while sewing so that it would curve better...then sewed on the back pieces
* I added a vertical stripe and an anchor applique by freezer paper stenciling it onto the fabric
I found this sailboat home dec fabric when I was in Portland a couple weeks ago at Fabric Depot. It's a good thing I don't live in Portland - our fridge would be empty in order to buy all the cute fabric there.