Hi Mojo420, welcome to the site.
What do you want to know? How to actually create custom Interfaces, or how to use ones created by other people?
Realize that we can't actually give you any specifics for LotRO yet as it is still in Closed Beta and thus NDA (non-disclosure agreement) rules apply, but a general overview of Interface customization as seen in other games can be discussed.
"My friends, love is better than anger. Hope is better than fear. Optimism is better than despair. So let us
be loving, hopeful and optimistic. And we’ll change the world."
Co-Founder & Admin: MMOUI
Avatar Image by RafM