icinga2-vim
https://github.com/Icinga/icinga2/tree/master/tools/syntax/vim
Clone fromIcinga 2 Configuration Vim Syntax Highlighting
$ PREFIX=~/.vim
$ mkdir -p
Modify 'ftdetect/icinga2.vim' if your configuration isn't located in '/etc/icinga2'.
Now test it :-)
$ vim /etc/icinga2/conf.d/templates.conf