I am apologizing in advance as I'm going to step on people's toes here and repeat some stuff, sorry.
OK, first thing I would do is swap out the Befouls for Eradicate (Urza's Destiny), what you lose in versatility you gain in the ability to Lobotomize a certain creature from someone's deck, making the Living Death a little better for you.
Next, swap the Urborg Elf for Llanowar Dead. You don't need the blue mana, but the bigger body could be of use. And squall is better off as Squallmonger.
Since you are running Buried Alive, run more big creatures in here. I'm guessing that your collection spans from Masques forward, so maybe you have access to Avatar of Woe (highly recommended in here), Spiritmonger, Fallen Angel (huge in here) and big green creatures. But you should not have a difficult time at all finding a big green and/or black creature to add to the beatings. Oh, yeah, Blastoderm wouldn't be bad at all in here.
I guess it really depends on what you have. I would say the key to making the deck work is to build around the Living Death, try to make every card in the deck make Living Death a better cast. That means you need:
1 - Graveyard fillers: You've got the Buried Alives and Living Death, that should do it
2 - Utility creatures: You've got Quagmire Druid (a good call for this deck) but you need more. Consider some good '187' creatures (creatures with come-into-play abilites) as you will get 2 uses out of them at least. I'd look at the Urza's block echo creatures like Bone Shredder and Yavimaya Granger as their suicide ability isn't bad in here. But their are tons of other great ones to consider; Spike Weaver, Woodripper, Yavimaya Elder, Nekrataal, Eater of the Dead (look him up if you don't know what he does
www.crystalkeep.com) and more.
3 - Big creatures: I Penumbra Wurm isn't enough, you need more beef, especially with the Buried Alives.
4 - Suicide engines: You want to be able to quickly kill all of your creatures so you can Power a huge Living Death. Best done be Fallen Angel and Phyrexian Ghoul, but Phyrexian Tribute, Reprocess, and Diabolic Intent also do a good job.
5 - Support: This falls on permanent removal and utility. A lot of this can fall into the hands of your creatures if you choose wisely, but I would at least include Eradicate or Tormod's Crypt, not both though. The key is to run as many creatures as possible.
If you use these 5 points as guidelines, you'll be able to build a deck that can own the game if the Living Deaths go off, and completely hold its own if you never see the L.D.
Hope this helps.
