CentOS 6.0

<OS>-<OSVERSION>-<NAME>_<VERSION>_<ARCH>.tar.gz
(just see our templates for an example)

and yes, all templates which are not provided by our downloader are unknown, as they just miss our description file - but this is just a minor issue and does not prevent you to use it successfully.
 
It would be great if you added it to your own repository - then it would appear in the ProxMox web interface for download. I'm sure you have a lot of users who prefer this less technical method.
 
added to our todo list.
 
On the proxmox host:
Code:
cd /var/lib/vz/template/iso
wget -O centos-6.0-standard_6.0-1_i386.tar.gz  [URL]http://download.openvz.org/template/precreated/centos-6-x86.tar.gz[/URL]
Then append to the file:
/var/lib/pve-manager/apl-available
the following lines:
Code:
Package: centos-6.0-standard
Version: 6.0-1
Type: openvz
OS: centos-6.0
Section: system
Maintainer: OpenVZ Development Team <[EMAIL="openvz@openvz.org"]openvz@openvz.org[/EMAIL]>
Location: [URL="http://download.openvz.org/template/precreated/centos-6-x86.tar.gz"]http://download.openvz.org/template/precreated/[COLOR=#222222]centos-6.0-standard_6.0-1_i386.tar.gz  [/COLOR][/URL]
Infopage: [URL="http://pve.proxmox.com/wiki/CentOS"]http://pve.proxmox.com/wiki/CentOS
[/URL]md5sum: 1234567890abcdef1234567890abcdef
Description: CentOS 6.0 (standard)
 A small CentOS 6 system including all standard packages.

Replace the md5sum above with the actual one and the download URL where you have renamed it. The leading space in the last line is intentional.