Making a good atmosphere and when we say good we mean creepy and dark is the key to have a good zombie theme party. If you have the chance dim the lights if not getting some colored light bulbs will do the trick ( brown and red should do the trick ).

Make the place crawling with blood hand prints. You can use water colors, food coloring or anything similar and just dip in your hands and start smearing! Alternatively if you can't afford to mess up your house you can always opt for blood smear stickers.

Throw in some body parts. If you have some old pants and shoes making some of your own should not be heard. Take some fabric and roll it into a, well roll and tie it up. The diameter of the roll should be about the same as the diameter of the human leg - this makes the base of the leg. Put the shoe on on the one side and dress the roll with a part of the pants - tear the pants a little bit to make it look like the feet was munched upon. Spill some fake blood over it.