all my wallpapers are black
It's not for the reason you might think.
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My first laptop was a Lenovo something-book I can't recall. It boasts an Intel i3, 500 gigs of HDD, and most importantly a fantastic display. With barely any HD quality in it, it belongs to a category of screens that makes you doubt if the color black you are seeing is even black. I must place some respect to its name although what I went through was.. well, euphemistically, a ride, deserving enough for another post. The constant frustration with crashes and slow loads led me to an obsession for maximum performance. I cut down unnecessary apps/software, pre-installed Windows apps, use respectable brightness level, and energy saver. Add that with my fantastic display, I simply couldn't find any images well enough to serve as my wallpaper. After trial and error, I eventually gave up and chose the most boring option, black.
What can I say about it? It just works. I don't need a perpetual reminder how horrible the screen is. I just need it to work. But I went further than just adopting a black wallpaper, I hid everything on my desktop and made everything only accessible through file explorer, taskbar, or search bar. It's how I feign ignorance to how much the screen sucks. (A credit to the digital minimalism movement because that's how I first learned that you can hide the desktop icons).
Since then, even after getting a new, better laptop by a large margin, the habit never left me. I have gotten so used to a black wallpaper that any images as a wallpaper weirds me out or just never holds up long. The habit branched onto my phone wallpaper choice. So minimalism was never the main reason; it was my pedestal.
I am totally not advocating for black wallpapers.
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If you ever need to test a display's quality, I think you ought to see how it fares with the color black. Nowadays I like to admire with how black my wallpaper is (though I can still see a faint blue in it) thanks to the now, better display. It's 4k or something.