Nice belt, I wish I could make something like that. I'll second belofalbion and Danielle, it might look even better with just one colour or leather lacing.
I'd also be really interested in knowing your source as well. As a student of a druidic path myself, it's quite frustrating trying to sort out the accurate information from the fluff, but unfortunately where the Celts (and especially the Druids) are concerned, there seems to be a great deal of shoddy scholarship.
The concept of a purely druidic writing system doesn't make sense because as Caesar noted, "The Druids believe that their religion forbids them to commit their teachings to writing, although for most other purposes, such as public and private accounts, the Gauls use the Greek alphabet. But I imagine that this rule was originally established for other reason - because they did not want their doctrine to become public property, and in order to prevent their pupils from relying on the written word and neglecting to train their memories; for it is usually found that when people have the help of texts, they are less diligent in learning by heart, and let their memories rust" Not that there's any problem with a neopagan druid using runes or ogham, it just seems that the paleopagan druids didn't.
If you're looking for sources on the druids, ADF's recommended reading list for dedicants has some decent ones: http://www.adf.org/training/resources/reading.html
I personally really enjoyed Ellis' "The Druids".