Change Default Cover/Album Art

Been googling all night how to change the default cover/album art in itunes 10 from the boring grey music note to something else, but there really doesn't seem to be a solution. I'm looking to get the location of the default cover art and replacing it with another one so that any song added without a album art will receive the new "spiffy" album cover, or at least something along those lines. Thanks for the assistance.