I also tried using an unsupported locale (en-GB in my case) the first time I installed the appliance, so having them documented would be good.
Here are a couple of other things I found useful:
If installed under Hyper-V, run:
yum install hyperv-daemons to make keyboard input behave properly in the Hyper-V RDP session to the Linux text console. Otherwise it's a bit random whether a character typed on the keyboard gets seen by the Linux kernel. (This seems to be a problem with Linux on Hyper-V in general - it's even worse on systems where there is no feedback when typing a password!)
Set the time-zone to make the date and time strings in the logs more relevant to your location. This is controlled by the /etc/localtime file, which can be a copy of, or a symlink to, one of the time-zone files in /usr/share/zoneinfo. In my case, I used a symlink to the Europe/London time-zone file as follows:
ln -snf /usr/share/zoneinfo/Europe/London /etc/localtime There is also a time-zone name stored in the /etc/sysconfig/clock file on the line beginning "ZONE=". I edited that to use the same time-zone name. (I think it is used by CentOS's "system-config-date" utility, which isn't installed by default in the ERA applliance, but can be installed using yum. It has quite a few dependencies though, so probably not worth it.)