Infect deck

Welcome to the site.  Sadly there aren't too many of us that offer input on deck ideas, but I'm sure I'm not alone in saying that we'd welcome any and all input.

So the first question that has to be answered is what type of playing does this see?  Competitive at your LCS, Casual one-on-one, Multiplayer?  The reason I ask is because there are a lot of different ways to take this.

Beyond that, how much have you played with the deck?  Have you had a great deal of success or are you getting dropped on a pretty regular basis?

My first reaction to what you have pieced together is that there are some solid pieces, but also some perhaps not so strong ones.  I like Plague Stinger, Hand of the Praetors, Reaper of Sheoldred, and Skithiryx, the Blight Dragon as they all really fill some increasing needs as the game would progress, with the Stingers giving those first few poison counters, Hands pumping up your creatures and giving you a means of directly putting more poison counters on them, Reapers giving you a really nasty defense to make them think twice about attacking, and Skithiryx as a sort of end game creature.  However, beyond those, I think the creatures could really be reworked.  Namely, Septic Rats are good, but they are easily blockable and don't do much if you don't already have a poison counter on them.  Blackcleave Goblin doesn't give you much for a four-drop, as a 2/1 can be killed really easily.  Phyrexian Swarmlord and Blightsteel Colossus can both be game enders for you, but your likelihood of winning is significantly reduced if the game goes on long enough for you to get either of them out.

Why pull in green rather than blue here?  Blue gives you access to some NASTY infect mechanics via Blighted Agent, Thrummingbird, and Viral Drake.  The Agents give you a guaranteed poison counter per turn, Thrummingbird gives you a "get in the way flyer" or can let you proliferate, and Viral Drake gives you another flyer who can proliferate without you even having to attack (or even proliferate more than once per turn).  Further, blue gives you some sorcery, instant, and enchantments that can really help speed up an infect deck (as you need to kill them quickly or you'll lose your advantage).  Steady Progress is a nice card to throw out on their turn if you have some left over lands, as it proliferates AND lets you draw another card.  Inexorable Tide essentially ends the game when it comes out.  Also, if you want to stick with the Blightsteel, you can include Shape Anew to rip him out on turn five, as opposed to around turn ten.

For the artifacts, Decimator Web is good, but you could also throw in Contagion Clasp and/or Contagion Engine as both of those help proliferate too.

I hope those ideas help.  Let me know your thoughts and I can try to help more as you move forward.