These two wiki entries may be useful to you:
Formatted_Numeric_Data makes use of IBM's ICU to display values in various locales within Cegui. This includes the format of numbers (123,456.78 versus 123.456,78), currencies, local to/from GMT date and time conversions and other gooddies.
There also has been a thread on the subject of creating a multilingual Cegui application. If I remember correctly a language file is read and as a .layout is loaded the labels are changed to the appropriate values for the language. One day it will be found and wikied into an article; this is an important topic for me.
DynamicFont and
GameChatBox demonstrate how to use true type fonts in such a way that you can change their size easily i.e. create an arial 10, arial 12, arial 24 without having to manually create .font files.