My original plan was to remove the thumb and have the four fingers signify that this was the fourth volume of Dolor, but then this would've just been the Left 4 Dead cover, wouldn't it?
ADDITIONALLY: Thank you for the emails regarding spare postcards. I have addressed one to everyone who messaged me and I'm on the way to the post right now. MICA Illustration students, I still haven't put these in the office, but I'll put something on twitter when they're there. Get off my case.