Bae'zel
Hero
For sure, there’s been darker portrayals of Fey: Ridley Scott’s 1985 Legend, for example.This isn't really one single aesthetic. It ranges from the saccharine to the grimdark.
Also Suldrun’s Garden by Jack Vance. We get in hard rated R content in there.
Even certain books by Neil Gaiman (yeah I know, but this isn’t a promotion) contained examples of darker Fey-adjacent themes.
Making Goblins into Unseelie Fey makes them darker to me overall, based on the fiction and folklore I’ve experienced in the past.