You can festoon your apartment with all the dollar-store cobwebbing you want, but it's atmosphere that'll make or break a good Halloween party. Over-the-top decor and a spot-on music playlists are, obviously, crucial. But we'd argue a few carefully chosen background visuals go a long way. After all, nothing makes a better conversation piece than an out-of-context, deeply WTF-inducing video clip caught out of the corner of your eye.