Two of my favorite and (IMHO) more profound Celtic symbols for freedom:
The hawk was considered an animal symbol of victory and freedom to the ancient Celts. It is typically depicted in Celtic art clutching or devouring a rabbit which was symbolic of lust, greed or frittering away resources to the Celtic symbolic mind. Philosophically, we could interpret this symbolic illustration as freedom (the hawk) from limiting behaviors (rabbit). I’ve written a bit on the symbolism of the hawk (in general) here.
In the Ogham, we find the Ur (or Heather) is considered a legitimate symbol of freedom in the Celtic language. Specifically, the Ur indicates an outpouring of the soul, a release or catharsis. Once the inner conflicts have been expelled, we are free to express ourselves with effective clarity.
Other pages of interest: