They are beautiful, aren't they. Used these Celtic patterns and designs when I did Calligraphy.
I have always loved Celtic mythology - all the Scottish and Irish heroes and legends along with our own King Arthur (English) and Merlin (Welsh) - the wonderful Arthurian and Grail...
I've always enjoyed how intricate some of the knots are, and how some seem neverending/infinite. The designs are gorgeous.
The only tattoo I have at the moment is a bit of knotwork on my left wrist. :)