I got curious enough to look for the source and roped my partner into it by accident. Feel free to read ahead for some vaguely nerdy rambling.

Between my partner and I, we believe we've tracked down to the specific LoRA that was used to generate this image (yes, it's almost certainly AI generated). There's a few very, very similar images floating about, some of which have more obvious artifacts; in this image, one of the bigger signs is the mess of indistinct orange shapes in the bottom right corner. Other images have multiple water levels, varying number of toe beans, etc. According to the LoRA description: "There is a certain chance to draw extra legs." Tremendous sentence. It turns out there's also a similar LoRA for dogs.

There's a video on BiliBili showcasing this wallpaper (you can find it relatively easily with a reverse image search), but we can't see enough of the comments to get information and looking further into that is a bit too much of a hassle. We're still unsure who specifically made it (the video comments do discuss this, but they cut off before we can read any potential answer), only that it was likely made by a Chinese internet user. If someone was curious enough and able to read them, we would be really curious about what the rest of the comments say. Edited to add: the video came out after the Steam upload that OP shared, and that is the earliest instance of this image that we've found as well, so it's certainly possible that is the source (though there are multiple other uploads of the same or slightly modified wallpaper on Steam as well).

Please do note that I don't intend on commenting on the ethics of the generation of these images, only sharing what we've found.