After seeing this hilarious Left 4 Dead spray, I decided to make a few of my own. :p
First of all, the original picture of the hole in the wall is from here. Also, if you want to use any of these, use the download link at the end, don't download the pictures. PNG files aren't compatible with L4D, so you wouldn't be able to use them, they are just here to show you what I made.
Here is the template that I made (which I then used for the rest of these).
Funny face (I made 2 because I couldn't decide which one looked best.)
Umm... I'm not sure if this is human...
A HL2 zombie
A heavy from TF2
And, of course...
Okay, maybe I went a little overboard... but it only took like an hour to make all of these. :p
So now... You can download all of these sprays here. I have also included the template (in both XCF and PSD formats) so you can make your own.