Hey,
First, I apologise for my english, and I hope it is understandable.
I am doing researches on the use of "classical" paintings in (espescially black) metal album cover art. I am looking for : simple use of these paintings (like the cover of Blood Fire Death), use of these paintings with modifications (like Anthem to the Weilkin at Dusk or most of Summoning's albums) or just inspiration from iconic paintings (inspiration for a cover artist, or just one cover art that refers to a painting).Can you bring me examples of this ? Whatever genre you want (even if iam most interested in Black Metal) the more I can find, the better it is.

Archives of Khazad-Dum may be relevant to your interests. It's a blog that kinda-sorta catalogues the use of pictures and paintings in metal artwork, both untouched and as inspiration.

http://archivesofkhazad-dum.blogspot.dk/

At least one of these examples is covered by the site above, but off the top of my head...

Cradle of Filth's latest album Cryptoriana has cover art inspired by The Birth of Venus.

Blessed Are the Sick by Morbid Angel and A Tribute to Insanity by Hexenhaus both used the same old painting as cover art.

I'll assume contemporary artists are okay, as Blood Fire Death's author is relatively recent.

Black metal:

Armagedda - Ond Spiritism/I Am
Every Grand Belial's Key album.
Der Stürmer - Crushing The Maccabees
Damnation - Destructo Evangelia
Necros Christos - Nine Graves/Doom Of The Occult
Peste Noire - La sanie...
Sadogoat - Cultus Capriea
Sigh - Scenes From Hell and In Somniphobia
Parabellum - Sacrilegio
Absurd - Facta Loquuntur/Der Fünfzehnjahrige...

Death metal:

Every Arghoslent album
Bolt Thrower - The IVth Crusade

That should give you an idea or two. I also suggest looking into Timo Ketola's works, all of them have this classic aura as he usually paints them in oils. Like a stale breath from a demonic medieval coffin.

Deicide- Till death do us part

Chakal-Abominable Anno Domini

Are you just after paintings or do printmakers count? because Gustave Doré probably has more credits than any other artist when it comes to his work being appropriated by metal bands.

Ahab - The Divinity of Oceans
https://www.metal-archives.com/images/2 ... 231990.jpg

Cryptopsy - None So Vile
https://www.metal-archives.com/images/1/9/9/199.jpg

Anathema - The Silent Enigma
https://www.metal-archives.com/images/1/6/0/8/1608.jpg

I will add more..

Burzum used a few. Celtic Frost - Into..., Hate Eternal, first album. There must be many. Gorgoroth and some other band used the same one.

Gorgoroth - Instinctus Bestialis --- Christ In Limbo by Hieronymus Bosch (right upper part of the painting is on the album cover) https://d32dm0rphc51dk.cloudfront.net/PvOQKjsl6mklPIgl7kxvAA/larger.jpg

Burzum - Filosofem --- Op under Fjeldet toner en Lur by Theodor Kittelsen https://en.wikipedia.org/wiki/Filosofem#/media/File:Filosofem.jpg

Burzum - Hvis lyset tar oss --- Fattigmannen by Theodor Kittelsen https://en.wikipedia.org/wiki/Theodor_Kittelsen#/media/File:Theodor_Kittelsen_-_Fattigmannen,_1894-95_(The_Pauper).jpg

Burzum - Fallen --- Elegy by William-Adolphe Bouguereau https://en.wikipedia.org/wiki/Fallen_(Burzum_album)#/media/File:Burzum_-_Fallen.jpg

Ghostbath - Funeral --- Ophelia by Sir John Everett Millais https://en.wikipedia.org/wiki/Ophelia_(painting)#/media/File:John_Everett_Millais_-_Ophelia_-_Google_Art_Project.jpg

Peste Noire - L'ordure à l'état pur --- La Liberté guidant le peuple by Eugène Delacroix
https://www.metal-archives.com/albums/Peste_Noire/L%27ordure_%C3%A0_l%27%C3%A9tat_pur/307396
https://upload.wikimedia.org/wikipedia/commons/5/5d/Eug%C3%A8ne_Delacroix_-_Le_28_Juillet._La_Libert%C3%A9_guidant_le_peuple.jpg

Thank you all for all of these replies ! Archives of Khazad Dum looks awesome !