Monster Magazine Covers
Here is an incredible collection of pulp magazine covers of the horror variety. From Creepy, Eerie, Tales From The Tomb, Nightmare, and many other titles, there is a great selection of horrific and fantastic covers to check out here.

Fletcher Hanks
Fletcher Hanks comics are filled with rigidly drawn characters battling bizarre forces with powers that are both Godlike and surreal. The use of primary colors in most of Fletcher's comics only adds to the strange dreamlike atmosphere of the stories.
Scroll to the bottom of the link posted above to see 3 Fletcher comics. Below you'll find links to various Fletcher Hanks comics. Unfortunately there's pop ups in a few of them, so beware.
Stardust The Super Wizard from Fantastic Comics #1
Stardust Vs The Emerald Men
Stardust in Fantastic Comics #6
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Stardust The Super Wizard from Fantastic Comics #13
Stardust in Fantastic Comics #14
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Stardust in Fantastic Comics #16
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Fantomah
Another Fantomah Comic
More Fantomah

Thanks to Rob Lashaw for many of the links.

Virgil Finlay
Another great artist associated with pulp comics, Finlay's intricate linework is comparable to the likes of Gustave Dore or Albrecht Durer. 

See Datajunkie's posts showcasing scans of Finlay's art by click the following numbers... 1 2 3

Click here to see an illustration Finlay did of a Lovecraft story, part of which can be seen above.

War Of The Worlds
Carrying on with the pulp art, here's a great collection of artwork related to the H.G Wells story "War Of The Worlds".

Frank R Paul
2nd Gallery - Scroll through the pages below to see additional work.
3rd Gallery
4th Gallery
Many high quality copies of Paul's black and white illustrations have been posted over at Datajunkie.
You can find more artwork by Frank R Paul along with other pulp artists at this gallery.

Thanks to Hyperdave at Datajunkie for bringing this artist to my attention.

Hasama

Rodney Matthews
Matthews has created many paintings exploring fantastic landscapes with alien monsters and strange technology, usually in some form of conflict. His interpretation of trains and cars are very bizarre. Click here to see a second gallery of his work.

Richard A. Kirk
Many strange pictures to be found in this gallery. The running theme in much of the work is a very grotesque mutation in the human figure, from completely abstracted facial distortions such as this, to the golem sized beast in this image. The pictures are incredibly detailed and the ink washes in the gallery section are amazing.

Link found thanks to Huge Strikes Back!

De Es Schwertberger
Although best known for his paintings of rock like characters, I think his best work is that influenced by Ernst Fuchs. Click the following numbers to see what I think are the best De Es paintings. It is unfortunate he isn't making work like this anymore.

1 2 3 4 5 6 7

Theodor Kittelsen
Kittelsen made many fantastic illustrations of characters based out of fairytales and legends. Images such as this and this one depict very nightmarish and haunting creatures lurking about. This image of humanoid creatures made from mounds of hay is especially disturbing.
2nd Gallery

Artist found thanks to BibliOdyssey's link to this gallery of Trolls. Check it out to see more work by Kittelsen.

I found this strange drawing of a giant skull face made from strange landscapes and buildings. It appears to be artwork for some band called "Sileni"?

Erik Desmazieres
The image above is an aquatint etching based on "The Temptation Of St Anthony" by Jacques Callot which I've linked to a few times on Monster Brains. The sprawling landscape filled with monsters as far as the eye can see, this is the kind of artwork I live for. I imagine Joe Vaux has probably seen this one. Be sure to check out the following links to see more work by this artist.

2nd Gallery
3rd Gallery

Ho Baron
This gallery contains a wide selection of surreal bronze sculptures that define strange objects and characters. There is an ancient and often Lovecraftian vibe about much of the work.

Site found thanks to The Lumper.