I made a full 10vs10 server long time ago, with many plugins from here and many bug fix, recode, and new fun features with usage of custom extension and database.
I had no time to play and maintain L4D2 server, so I left everything.
I found my code today, 2 year later, and I think it will be cool to share my work.
This was not intended to be shared when I coded it, so excuse the bad comments, I didn't reread the code today.
There is 2 version:
The first is the original Free Arena server I made: http://gitlab.phangos.fr/sourcemod/free-arena-l4d2
In my point of view, it's the best, try the deagle headshot, rocket jump and gift spawning!
The second is a remake, for Zombie 4 Ever server (a friendly server), There is maybe some improvement and better coding style, but if I remember well they didn't want all the original features: http://gitlab.phangos.fr/sourcemod/zombie-4-ever
There is no database support in it, and new extension to get the randomness of item.
Ask me if you have trouble with something or if you want some help. Maybe I remember what I did ;)