Marvel Zombies was a miniseries showing the Marvel Universe after a zombie apocalypse turned all its beloved heroes into the walking dead. It's the brainchild of Robert Kirkman, who's become the king of zombie comics with his excellent ongoing series The Walking Dead (featuring art by Charlie Adlard and Tony Moore.)
The covers, painted by Arthur Suydam, were parodies of iconic Marvel covers...featuring the heroes as the undead. It's some mighty good lookins, Marvel comics fan or not. This site here has collected the covers from the miniseries and its tie-ins. Enjoy!