Okay, I'll try my best, though be forewarned that Suicide Black has been completely dismissed as being at all competitive in
tournament Vintage. I'll also attempt as best I can to respect your request to be nice.
First of all, traditional Vintage Suicide decks are based off disruption. Obviously, this is the casual forum, but it might not be a bad place to start. Duress, Hypnotic Specter, Hymn to Tourach, Sinkhole, Null Rod, and Wasteland are all common sights.
As for your mana base: If you don't need the Wastelands, that's fine, but Phyrexian Tower and Cabal Coffers are worse than Lake of the Dead, which also isn't that great. The most glaring ommission, though is no Dark Ritual. I don't care if you completely ignore everything else I say--but you
need 4x Dark Ritual!
You also have a lot more creatures than the average deck runs. You know that an opponent gains control of Sleeper Agent when it comes into play, right? As in you can't attack with it? I deals them 2 damage a turn, and you three damage a turn. With the exception of Wall of Blood, you don't seem to have any way to negate the Agent. I woudl prefer Wall of Souls in that slot anyway, or even better, no Walls at all. You're not running the two most effecient black attackers ever: Phyrexian Negator or Nantuko Shade. I'm guessing by your build that your group plays mostly aggro, so Negator is no good there, but the Shade still deserves a spot. Usually when people play Carnophage, they also play Sarcomancy. Flesh Reaver was another commonly used option back in the day.
As for the "Misc" section, there are two things that immediately spring to mind (well, other than the aforementioned lack of disruption). The first is that both Demonic and Vampiric Tutors are restricted in Vintage. The second is that there is no Necropotence or Yawgmoth's Bargain. If you configured the deck differently, Yawgmoth's Will shoudl be there too, but as is, it would be not-so-hot in this deck.
Finally, I ask the question: what environment exactly is ths meant for? If it's multiplayer, than cards like Duress, and its lesser counterparts Hymn to Tourach and Sinkhole aren't worth it, but even if it's casual one-on-one's I'd say go for some of those. If there is control, go with the Duresses, if it's all aggro, then don't. Are you respecting the Vintage restricted list?
I guess here's the part where I make my suggested changes. I'll try not to be too drastic, though, and will reserve judgment on some things, not knowing your style and all.
-2 Cabal Coffers, -1 Phyrexian Tower, -1 Swamp
+4 Dark Ritual
-4 Swamps
+4 Polluted Delta/Bloodstained Mire
-4 Sleeper Agent
+4 Sarcomancy
-4 Grinning Demon
+4 Hypnotic Specter
-2 Maggot Carrier, -2 Unholy Strength
+4 Nantuko Shade
-2 Unholy Strength
+1 Necropotence, +1 Yawgmoth's Bargain (more of these if you aren't using the Restricted List)
-2 Wall of Blood
+2 Diabolic/Chainer's Edict
I know that these aren't the absolute best you can do, but I am trying not to stray you too far from you original notion of the deck. A lot of people would be like "-60 these cards, +60 GiftsBelcher" or something and,
while I don't suggest you play this deck, if you are going to, maybe my suggestions will treat you a bit better than your previous build.
Also:
(also i couldn't find any good suicide deck)
There's a reason for that.
