if this is specifically a "goth party" or whathave you (like a themed party), then you might want to encourage dressing the part, both for the host and the attendees. also, yes, taking the extra care to deck the place out appropriately is a nice touch to add to the ambiance (assuming that how you normally decorate is not all that gothy, but even if it is, maybe lighting some candles, throwing out an extra decorative piece here and there, etc).
and yes, i'm a big stickler that parties always have the proper "soundtrack" going on at just the right background volume, just loud enough for some enjoyment and to make awkward silences less awkward, but also quiet enough to encourage discussion. i suppose the "type" of goth music would also depend on what sort of goth types (re: dress) would be attending, I.E. Rasputina and Voltaire for period goths and Skinny Puppy and Combichrist perhaps for a more fettishy crowd.
also, if there shall be the drinking of the alcohol, most goths go for the Absinthe, and even if they never tried it, a goth party is the perfect time to experiment. red wines work, too (in keeping with the whole "vampire" simile to goth or whatever).
If you want to show movies (many of my parties usually involve movie watching just because we all like movies), consider some old silent classics won't you? german expressionism goes extremely well in a goth setting, also, you can keep on your music if you want and people not interested can keep talking with out the viewers being too distracted from the film, what with it being silent and all.
soooooo, are you actually throwing a party and looking for ideas or just curious?
