Please find below some custom UIs shared by members of the LK SWTOR guilds. Feel free to download and use.
Locating, Installing and Using Customized UI Layouts
SWTOR custom user interfaces are stored as .xml files which can be found in the follow location:
If you are on Windows 7 or Windows Vista:
C:Users< Username >AppDataLocalSWTORswtorsettingsGUIProfiles
If you are still on Windows XP the path is slightly different, it's:
C:Documents and Settings<user name>Local SettingsApplication DataSWTORswtorsettingsGUIProfile