he is correct! Koops has a bandaid on his nose and that little blue hoodie

Good eye mate! I guess this makes this a triple cross-over?

Original artist here! I just submitted this, and if you have any questions for me, feel free to ask. Background: I've been wanting to do this poster for years, since l4d1 came out and never had a free moment. I only got around to finishing it a few months ago.
As an added bonus, here is the rough draft for this poster I made when l4d1 came out, notice it only has the hunter/smoker/witch and tank.
http://i.imgur.com/9mbsD.jpg