like, the earliest official key art we have of them had this very grungy feeling to it that reflected the unknowable-untouchable mystique that shadow milk had as a villain at the time; a calculated and genuinely unnerving antagonist figure who knew more than We did, and conversely we knew effectively nothing about Him. there was a very palpable power imbalance between him and pure vanilla evident even just from the small handful of interactions they had in beast yeast 2 and the tone of the art people made of them, even in the devteam, reflected this very readily. look at all these cool blues and negative space! this aesthetic fucking rules!!
compare this to around the time of fourth anniversary though and you see this very interesting shift; content surrounding shadow milk has become Visibly brighter and theres generally much more emphasis on Scale and Spectacle. thematically you could hearken this to anything from shadow milk finally coming out of the dark (both in a figurative info-void sense and Literally) and stepping into the spotlight on a stage of his own design, or in the case of beast yeast 8 it being pure vanilla shining a light onto his machinations proper, which reflects in how the fandom tends to approach discussion and conveying shadow milk's character since the Mystery is kind of Solved now in a sense
keep in mind of course that concept art is often inherently Different in intention from the final product in all cases of gamedev as its an exploration of visual elements that may not end up Sticking but for a LONG time the initial examples were really some of the only artwork milkshake fans had of the two and it REALLY influenced the shape of their earliest fanworks in a way that Cannot be understated. its an aesthetic that you really don't see now in favor/reflective of how devsis is much more out in the open about what this guy's Deal is (and with their more memefuck treatment of him as an effective game mascot), which of course was an inevitability as his story was unveiled, but its still a bit sad to see the sort of Cryptid Horror energy he initially had sort of get lost to time