You may be surprised about how many people like psychological horror, it's not an uncommon subgenre in that genre of film. Instead of making a bunch of promo material just make a few really good banners/posters that give people a hint of what your comic is about (With the title), and use those interchangeably along with some of your favorite pages.
There are a few tags you can use on Twitter that may help: #webcomics, #indiecomics, #makingcomics, #comics, #graphicnovel, #psychological, #horror, #darkart
If you're into horror you could also follow other horror peeps, like podcasts, artists, comic creators, novelists, etc. You could also follow comic reviewers (If you like their content.), as well as liking posts related to your medium and genre. I've noticed people tend to migrate to others who share the same interests, and the horror community is pretty into supporting eachother so you just need to find your groove. Also following other webcomic creators and artists whose work you like may lead you to promo threads where you can post your work.
If you haven't already go ahead an add your comic to the Webcomic Library. The submission form is in the profile.
You can also join a couple Discord servers. Webcomics Garden and Spider Forest. (The latter is mostly a private server, but there is a public portion you can access.) You can promote and talk about your work there, as well as make some good friends.
