How To Create a Custom Culture in Sitecore

1) Create a culture on the server and register it

http://msdn.microsoft.com/en-us/library/ms172469(v=vs.80).aspx

CultureAndRegionInfoBuilder cib = new CultureAndRegionInfoBuilder( “x-en-US-sample”, CultureAndRegionModifiers.None);

CultureInfo ci = new CultureInfo(“en-US”);

cib.LoadDataFromCultureInfo(ci);

cib.Register();

2) Install a custom culture (copy files and deploy registry keys)
http://msdn.microsoft.com/en-us/library/ms404375(v=vs.85).aspx

3) Create Icon files (for the right sizes in Sitecore)

4) Compress the Icon in a zip file

in the folder sitecore\shell\Themes\Standard\CustomFlags.zip

4) Create Custom Language in Sitecore (specifying dictionary, iso codes etc)