Our conclusion on the elite of the Black Arts.
Venom - Black Metal
Not just named the genre but with their lyrics and that unquestionably iconic face (with that sarcastic smile) of Satan they laid down the path for the future generations.
Bathory - Bathory
Technically the same as above but if possible Bathory raised the sinister atmosphere to a higher level. Indeed another iconic Black Metal cover.
Mayhem - De Mysteriis Dom Sathanas
The cover fits perfectly to the music, mysterious is the right word, and of course had a huge impact on the newcomers, many bands used mysterious buildings like churches, cathedrals and castles later on their album covers after Mayhem.
Darkthrone - Under A Funeral Moon (or any of the Unholy Trinity)
Corpse painted member on the cover. Familiar? Not just in terms of music (Transilvanian Hunger) but in presentation too Darkthrone is possibly the most copied black metal band of all time.
Sarcofago - INRI
Spike Kult! 4 warriors in front of Christ, the pictorial representation of Southern Violence and clearly an undeniable influence on a huge part of the third world countries.
Blasphemy - Fallen Angel Of Doom
The archer goat drawing, white on black with red logo and title, main source of inspiration for later artists like Chris 'Thorncross' Moyen.
Beherit - The Oath Of Black Blood
Well the aforementioned Chris Moyen indeed is famous of his goats but his most iconic cover doesn't have any but a group of satanic skeleton priests as conducting a black funeral or summoning something horrifying from the deep. Same, white on black with red logo and title.
Emperor - Emperor / As The Shadows Rise
2 early usages of fine art engravings by mastermind Gustav Doré, later this type of engraves became one of the most used in the genre. (after the photos of corpse painted black metal warriors).
Marduk - Opus Nocturne
The earliest Verwimp work he made for a band appeared immediately on a Black Metal record, and the result we all know: many famous (Black) Metal covers from him. - In this case we have to mention In The Nightside Eclipse too but Wahlin had a same or even more big impact on (Scandinavian) Death Metal too.
Impaled Nazarene - Suomi Finland Perkele
Simple and effective, the usage of a symbol with a clear message as album covers later became a common thing.
+1 honorary mention:
Mütiilation - Black Millenium
Wheelchair Kvlt (knowing the music, the lyrics, and the overall atmosphere no questions left I suppose).