I had a really hard time deciding between this album and Grave Digger’s 1998 album 'Knights of the Cross'. I ultimately went with my favorite (musically) of the two, 'Heart of Darkness' but you can still check out the art for 'Knights...'.
1995 was a crucial year for Grave Digger; the band found themselves releasing their darkest album to date, 'Heart of Darkness', where the band really honed a darker and more aggressive sound while their lyrics mirrored the intensity of the sound creating an all around more dismal experience for the listener.
Pre-Heart of Darkness days, Grave Digger experimented heavily with the art they would use for their covers. Anything from a beefed up Donald Duck (seriously) to a War Games inspired etching would adorn the band’s covers, but starting with the album The Reaper and continuing on through the most recent albums, the band exclusively used their Grim Reaper depiction, much in the same way Iron Maiden utilized the iconic ‘Eddy’. Though the said motif has been used in the two albums that proceeded ‘Heart…’ it was on this album that the character took its most solid and dark form in a way that would pave the way for the albums after.
If you would like to learn more about Grave Digger or sample some of their music you can visit their myspace here -- but I would suggest looking into their early works first by way of youtube where you can find complete playlists of almost all their albums.