Zombie Walks increasingly occur around the world. Zombie walks are public gathering (or flashmobs) of people dressing up as zombies. On the 13th of May, such a zombie walk occured in Moscow, with lots of really scary disguises being shown. There are several sites with pictures showing this event, some might even provide you with inspiration for scary halloween costumes.
For example, lots of pictures showing cool makeup, masks and costume ideas can be found at: http://englishrussia.com/2011/05/16/moscow-zombie-parade/