It has its charm. Like a scenery in the process of being formed in someone's imagination.

I really enjoy that, it seems like it's combining mountains and waves.

There are both mountains and water on the album release with other picture on album cover (found out it 'accidentally' when read this thread - viewtopic.php?f=1&t=71415&p=1678379&hilit=Ultima+Thulee#p1678379), so not so much left about imagination for me). :)

Hmm.. it's a difficult question for me, there are many favorites out there in my favorite metal genres (doom and black) and it's so hard to pick only a few.
I think I'll just mention what the first came to mind - it's Mandy Andresen's work on The Slow Death's debut - it's a concept album, and it has the concept album cover art with a lot of small details and more "atmospheric"/less detailed (but also very "moody"/dark) concept album art in the booklet pages, - love the album art, both of these styles, and also often use the styles myself (even though I don't draw that well).

Man, I like the other cover better.

I'm a sucker for album covers that are a painting of a wide apocalyptic scenes.

Satyricon - Dark Medieval Times
Iron Maiden - Somewhere in Time
Emperor - In the Nightside Eclipse
Dissection - Storm of the Light's Bane

I've been listening to Among Majestic Ruin by Morgion a lot lately, and that's a great cover, but then Solinari is even better. Two totally different approaches, both very esoteric and evocative, plus I just love yellow covers: