i'm not sure if your still looking for answers,, but i'm still happy to help.
1. what happens at a witch house show?
i have never been, but i have a good idea of what happens. loads of different clashes of scenery, using occult themes and loads or concepts and colors/imagery. let's say it's like a dark mythological rave. but that's just one interpretation of it.
2.what kind of fashion is seen?
lots of purples, blues, reds, definitely some of the stuff you added like crosses, triangles, also circles, different creatures of the night, foresty themes. and dark + pastels.
3.How does witch house make you feel? What kind of imagery does is make you think of?
minotaurs drinking tea, white shadows, black kittens, white leather. forests, different creatures... i feel like a mythological creature myself.
you should probably listen to your clients work, study them specifically. see what their imagery use is like.
hope this helps and i'm not too late.
my music is like a gothic forest rave, with minotaur lords sipping tea, sirens making out with satyrs and dryads ridding fauns that play with knives and fire.