I can't approve or disapprove this spray because I neither have or play L4D >.> But I can at least give some constructive feedback! :3
In my opinion, it's just a bit too brightly colored and solid to fit into L4D; Try using some more faded colors on the checkmarks and "X" and add some worn off spots. It'd be pretty much perfect if you did!
This is pretty funny, too. It wouldn't be the case for me though, I suck at L4D xD But anyway, there are some people that can glide through Expert (cough no lives cough) and I respect them.
That's pretty much all I have to say... Except what does "Infected Anger Level" mean? :S