It manages to look both industrial and organic at the same time. The black could be a scar or a burn, those could be human hairs stuck to wounds, definitely the impression of bloody abrasions, the background is vaguely human skin color. Or it could be paint peeling off the wall of an abandoned factory.
This picture from the same page you linked to in the OP appears to be mostly tree bark and wood textures, so now I’m wondering if that’s also the source of the cover art.
I thought it was mud on a dirty floor. I can be pretty literal at times.
Spoilered for what it actually is:
[spoiler] The Downward Spiral - Wikipedia
Turns out I was pretty close. I’ve done similar personal art projects. A close up view of a dirty napkin can become a dozen things in a dozen people’s eyes. [/spoiler]
My impression of the art, combined with the title of the album, is of some sort of damaged spacecraft in a death spiral orbit over some alien world.
Like Quiksilver points out, there is a large human (gorilla?) face in the upper right area of the picture, looking down at the black alien mass. There is also what appears to be bloody residue hanging from the face itself and from the limbs. What I get out of that is evidence of a struggle, violent struggle, with the end result being this disturbing black mass being ripped out of the insides of this person. Considering the theme of the album, it would make sense for the black mass to be representative of the sickness, the darkness, within the person and their ultimate victory in eradicating it. But, as the bloody wounds show, it didn’t come without fairly significant cost.
I know this is probably absolutely nothing and it’s just because the art was made so intentionally open-ended, lending itself to various individual interpretations. I am combining a familiarity with the music itself with my interpretation of the cover art.
It’s also harder to see details in the pics here vs on a large HD screen. But there are various figures and faces scattered throughout the picture. In one area in the lower right hand portion of the picture, what looks like a child being led by an adult can be seen. The child has a bright V emblazoned on his chest. I don’t know what that would be symbolic of (scarlet letter, of sorts?) but once I saw it I could not unsee it.
I don’t see anything other than a dirty wall that needs to be plastered and painted.
You mean to say you don’t see the big profile view of the face?
Looking at this 1500x1500 picture, nope. And I used to see a lot of faces in walls/ceilings when I was younger.
Ok, well look at it this way: You see those three spots of rusty looking blood (or something) that kind of form a triangle in the lower right side of the picture? Well look at the top red spot and it looks like a bloody goatee hanging from the chin of an apish-looking male face. Looking upwards from the goatee, you see the outline of the lower lip, then the nose area and then the big deep-set eyebrows.
This face is staring down at the menacing black tentacled mass. You see the left side profile of his face, as well as his left eye.
Using this interpretation as context, listen to this song and tell me I’m totally bonkers.
This looks like something that has been burned rather than simply stained. Looking at it literally, my first guess was that it’s the detritus from a session of drug use of some sort. Not ever having been a drug user, I admit that’s a wild stab in the dark, but that’s the first thing that came into my head.
Paul’s dead.
I had to google that. Ain’t no CT kookery here! 
My first thought was skin cancer so I guess he got what he intended.
I missed this post. That explanation of the artwork makes sense and more or less fits with my interpretation, IMO. Not exactly, of course but it’s art after all.
ETA: But I still see an unmistakable face in this cover. I don’t understand how anyone could not see it.
I see a bunch of crap smeared on a surface; said crap includes paint and blood and bugs and rust and wires. I don’t see any recognizable, let alone deliberate, shapes or forms.
But I’m intrigued by your description; can you maybe use Photoshop and mark up what you see so it’s more obvious to the rest of us?
A face? Really? Where?
Here is what I’m talking about.
