Finaly after 5 years a modder get to valve archive as a dev and bring them back to the show: The orginal l4d1 survivors. They can be download for l4d1 and l4d2. look on l4dmaps.com
For example, this mod [You must be registered and logged in to see this link.] works fine with my game, and many others too. Some custom maps(example:Urban flight) random crashed too. Maybe its because i have nosteam version,maybe problem with my computer,i dont know.