If you want horror comics and not necessarily Halloween-themed ones, look to Vertigo. Alan Moore's Swamp Thing is excellent and I have heard great things about Scott Snyder's Swamp Thing in the New 52 as well. On the topic of Scott Snyder, Wytches is superb, even if it's published by Image Comics. John Constantine: Hellblazer is also horror-themed (or the majority of his stories are), House of Mystery is also good, and the new DC zombies series coming out right now by Tom Taylor, DCeased, seems to be decent. Blackest Night, another zombie story, is one of my favorite events of all time, though if you're a new reader, it's probably not the best choice for you as it requires some background knowledge of DC and especially the Green Lantern mythos. However, if you want something that's already come out and has come out within the last year or so, I point you towards James Tynion's recent Justice League Dark. The series itself is not finished, but several trades have been released.
Hopefully those answer the question and provide some good horror recommendations, even if they're not explicitly Halloween-themed.
