For Teen Read Week in 2012, the theme was "It Came From the Library." The idea was to promote horror and thrillers, and I think this would be equally effective for adult marketing. Here's a sample of the promotional material put out by YALSA.
This could be adjusted to accommodate an older crowd. So many older readers have a fondness for (or at least remember) classic horror movies, so I think this phrase would play well to such a crowd. A display could be created using this theme, promoting classic horror novels and new authors like Justin Cronin and his Passage series. It would be no trouble to use integrated advisory here. The library could promote classic horror films alongside the fiction titles, as well as including any spooky non-fiction available. Devil in the White City by Erik Larson, Spook by Mary Roach, and Death's Acre by William Bass and Jon Jefferson would all be excellent non-fiction additions to such a display.