The truth about copyrights is that anyone that creates, records, composes, or writes any piece of work naturally owns a copyright.

However, registering a copyright with the Library of Congress makes it easier to prove your ownership/copyright in a court of law, should someone steal your work.

In other words, if you didn't write it, it is copyrighted, regardless of whether or not it is published.

Since you are not using this music or image to make money on this site and simply enhancing your story, you are probably okay to use it.

However, it would always be the recommendation of the owner of this site to get written permission from the original author.

For more information visit the Library of Congress.