I go for Mark Harrison's lovely pulp pastiche Dante cover, closely followed by Dom Reardon's Harry Kipling: you can practically smell the putrefying flesh on that one.
Link: http://www.2000adonline.com/index.php3?zone=covers&page=progs&FirstProg=1469&LastProg=1517&MaxProg=1517" target="_blank">2006: Cover to cover