Believe it or not, but the cover of Metallica's album Load actually has semen in it. This is an excerpt from the Wikipedia entry about Load:

The cover of the album is original artwork entitled "Semen and Blood III". It is one of three photographic studies by Andres Serrano created in 1990 by mingling the artist's own semen and bovine blood between two sheets of Plexiglas.

Apparently the artist who made the cover (Andres Serrano) did more with his own bodily fluids. Check out the Wikipedia article about that dude for more info.