You have to download the pack skin from Frosty who works for Turbine in the UI
department.
Curently book 14 skin is the latest and theres a preview skin for mines of moria skins but are not the final skins.
Every books update and if needed,the skins will be release in this section for the UI mods to download or anyone that wants them to fiddle with them.
http://www.lotrointerface.com/downloads/cat5.html