Of the cards available to you I think this is a decent setup. I wouldn't be concerned that you don't have a lot of creatures; 20 creatures is a decent amount. You may want to consider swapping out a few cards and increasing your land count to 24 though. I would probably drop the 2 Cellar Doors, the Demon's Horn and the Dead Weight for 4 swamps.
After that I would heavily consider bending your all-zombie-creatures rule to make room for the Grave Titan you have. He's close, he spits out zombies; he's just not a zombie himself. Trust me, you want him in the deck
If you DO make room for him I would also swap out 2 of your Ghoulraisers for 2 Gravediggers. Your 3 CMC slot is a little crowded and it's way better to choose the creature you get back instead of getting something at random.
Let us know how the changes work out!