Installing Multilingual User Interface (MUI) Language Packs on a Windows Server OS can be useful when you allow end users to log in on those system. This is the case in, for example, Citrix XenApp Servers or Remote Desktop Servers (formerly Terminal Servers).
This way administrators will have the benefit of eventlog descriptions in English which are easier to troubleshoot and run internet searches on, and quicker access to updates, but users will still be able to use an interface in their native language.
For this you need to find a Language Pack in .cab format. You can download an ISO containing every Language Pack available from Microsoft: Windows Server 2008 R2 Service Pack 1 Multilingual User Interface Language Packs (7601.17514.101119-1850_x64fre_server_langpacks_1-GRMSXLP1_DVD.iso)
Be carefull to download the correct ISO compatible with your OS and Service Pack level, otherwise you'll get an error message: "Language pack is incompatible with this version of Windows".