These are movies, but my favorite super symbolic artsy horror films are:
Pi (1998) About a guy who goes crazy looking at numbers. no film has induced a migraine within me as much. The ending is iconic.
Pig (1998) No one likes this movie, and if you're under 18 you definitely shouldnt see it. The whole thing is online for free. It's about a serial murder, and the whole thing is very very symbolic. It's very much in the same vein as Pi, just shorter and even more graphic.
^^ For these two the soundtrack definitely does a lot. A lot of the horror comes from anticipation, which can be difficult in a comic where anticipation means drawing a tooon of panels.
3 La Piel Que Habito- a medical horror story with really lovely cinematography and the weirdest film plot ever. There's a lot of rape scenes, but if you're looking for highly symbolic horror, I can't recommend it enough.
These are all films, but film and comic share a lot. Other than Ito, I don't know if I can recommend too many horror comics that legitimately frightened me, and even so I'm not terribly afraid of a lot of Ito's work (the comic that scares me is one everyone else thinks is stupid) i think concept and anticipation will do more for you in a comic than any scary picture ever will, because the scary picture can be avoided by just turning the page.