Old paper (more free images)
Found on flickr and free to use under a creative commons license are four great old, aged and wrinkled paper backgrounds. These would be great for treasure maps, invitations, letters of marque or other epistolary pirate paraphernalia (pirate things on paper), courtesy of bittbox.
Click here to see the set. To download one, go to the set, click on it, and then click on the "all sizes" button above the image.
Other free graphics previously mentioned:
Free Skull graphics
Free Scroll graphics