The deck that I posted was an old prototype, it's not really all that great compared to Scaredgirl's version (which is the one I use for Top 50 and PvP most of the time).
Bonewalls, Squids, and Plagues have been used, but most of the decks I see with them are over 30 cards, and all of them are slower than SG's.
It would be possible to remove a Bone Tower and add an Improved Plague, just as some creature control (if they have some annoying creatures on the field, such as Mind Flayer, Oty, Elf, etc., and you lack congeals), but it's entirely up to you.