Not sure how dark it looks for you but it's supposed to be quite dark, albeit not obstructively so. It's probably because my monitor is set on a slightly lighter than average setting, but I believe you should be able to pick out any detail that's essential (there isn't much detail to begin with).

(also, just to make sure, the image and all images to come are thumbnails linking to the full-size versions)

How about these ones?

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Anomaly

A quick, minimalist mood piece of an ominous Precursor space orb. Think about how unsettling it would be to encounter an object the size of a small moon that is perfectly smooth and featureless. And when you get closer and attune your sensors to it there's this noise, this feeling, in your head you can't quite place. Like a distant buzzing but more subtle, more indistinct. And it's like there's someone looking over your shoulder even though there's no one there and your ancilla can attest to that. Your armor can calm you down chemically, but the feeling of being watched just won't go away. You probe deeper and you start seeing things. Gray figures in the corners of your vision. Odd, surreal waking dreams you're supposed to be able to control and turn off at will. Whispers that are always one step away from being intelligible. Your armor or the ship are seeing or hearing none of this; it's just you. But you're drawn to the artifact. There's something unnaturally fascinating about it. And it's too late to turn back now, you tell yourself.

Next thing you know, you're in a medical facility with no memory of anything that happened after you approached the anomaly and they tell you they had to reset your brain back to several days before the encounter.

(This one is even darker than the first image, so I'm not sure how much any of it is visible with darker monitor settings.)

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Star Roads

This was actually the first piece I did and a very quick and crude one at that. The purple radiation is described as a byproduct of the Silentium-era star roads appearing from FTL but it also helps make them look more malevolent. (The purple tint of some of the stars is supposed to represent the way the active star roads' presence makes starlight itself feel biting and unpleasant, something that always struck me as a delightfully sinister detail.)

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Charum Hakkor

Here I toyed with the idea of Precursor strands made up of smaller intertwined filaments. Also shown are some basic ideas of what the ancient human structures built around them might have looked like (from the books, I actually imagine the orbital arches as being almost fully covered in human construction but I wanted to depict some of the base Precursor structure here).

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Trident

This piece was born after some consideration into how the orbital arches, star roads and the like would actually connect to planets. It started out as even more fibery, like the strands in the above Charum Hakkor pic, but I found that the smooth, almost bone-like texture worked better here. Even now it looks more "organic" than my usual mental image of Precursor technology.