I found Skin Mods for Left4Dead 1, 2 relate to the TV show called Futurama.
The First Pack for Left4Dead 1, 2 is: Philip J. Fry, Turanga Leela, Bender Rodrigue Professor Hubert Farnsworth.
Left1Dead version: http://steamcommunity.com/sharedfiles/filedetails/?id=154387516
Left2Dead version: http://steamcommunity.com/sharedfiles/filedetails/?id=158746431
The Second Park for Left4Dead 1, 2
Amy Wong
Hermes Conrad
Kif Kroker
Dr. Jonh Zoidberg
Left4Dead 1 Version: http://steamcommunity.com/sharedfiles/filedetails/?id=168301613&searchtext=
Left4Dead 2 Version: http://steamcommunity.com/sharedfiles/filedetails/?id=167980171