Anything can be a zombie-just some ideas:
Wear a bathrobe and hair cap, carry a back scrubber and wear some slippers.
A wedding gown.
A sports fan costume with your zombie face painted half and half the team colors.
A big hair 80s mall rat.
A rock star.
How to go about the zombie pallor:
SKIN: I use Elmer's glue for fake flesh. You can beef it up more by adding shredded bits of paper. Newspaper works well because it can become very fluffy. In fact, there is shredded paper in bags for paper maiche making in craft stores and that is ideal and powdery. Mix it into a paste with Elmer's and place it onto your face into whatever configuration of scarring or dead flesh you want. I like to do a mix--if I have a wound, I use the paper to build it up. If I plan to just peel back some flesh, I use the Elmer's. Put it on nice and thickly. Let it dry well.
MAKEUP: You can get makeup at the store that is already gray and ready to go for a base for your face over top of the fake flesh, but if you have women's makeup, you can rig this yourself. First, I suggest you take violet or purple shadow and dot it under your eyes, along the wounds you plan to make and then just mottle it around in finger sized dots here and there. Mix the woman's foundation with black or gray eyeshadow to make a nice gray tone to pat onto your face with a sponge. Where you want dead skin, peel back some of the glue. If you want a wound, take a toothpick and work an opening into the thick glue/paper mix and then take black eyebrow eyeliner or eyeshadow into the hole to make it look deep and nasty (see wound above) and add blood. For brusing, you can pat purple eyeshadow around the inner part of the wound opening and then around that, some green, then outside of that some yellow. This gives a bruise effect.
HANDY OPTION: There are things in your kitchen you can use for makeup including cornstarch, ketchup and ashes from some burned wood. In a pinch and at the last minute-you can decorate yourself from the kitchen if necessary.