I have been asked to make a bridal shower cake with a halloween theme, any ideas would be greatly appreciated.

You could make the sparkly pumpkin carriage from Cinderella.

OR

You could do one of those lingerie cakes and write something about the fiance falling in love with her "ghoulish" figure.

http://cakecentral.com/modules.php?name=gallery&file=displayimage&pid=1317303

Not "really" Halloween, more "Dia de los Muertos" but still appropriate, I think; How about a cake w/ the muertos (skeletons). One would have a top hat and one would have a veil, and you could stll add in other Halloween details, like jack-o-lanterns, or tombstones, etc.

Ah I guess this is when it's cool to be Goth... one of the orginals I might add.
Gothic bride on top of cake. colours purple and black or orange and black or black white and red. deocrated with black or red 'roses' cover base perhaps with black lace.

or maybe a pumpkin with a veil? or a cake with a hand (with lace sleeve) with an engagement ring