With it being St. Patrick's Day, it seemed like as good day as any to explore this notion by looking at some examples of this genre. The zoomorphic tradition is one which combines Celtic knotwork with intertwined animal depictions and this in particular seems of great interest. Here is an example of this tradition brought into the realm of vestments:
The sacristy of Westminster Cathedral in London has another example from this tradition in the form of a cope:
In point of fact, there was a revival of Celtic arts and crafts in the 19th and 20th century and in the area of embroidery specifically the Dun Emer Guild, who were based out of Dundrum, Ireland, produced a carpet that was presented to Pope Pius XI in 1931 and also produced a set of vestments for St. Patrick's church in San Francisco in 1923.
Also of note is the Honan Chapel located in Cork. The Honan Chapel is the product of the early 20th century Irish Arts and Crafts movement, inspired by the early 20th century Celtic revival. This particular chapel boasts Celtic inspirations ranging from the architecture down to the vestments.
A closer look at some of the details of the design shows clear inspiration from the Book of Kells:
One further example:
The Clonfert Diocesan Museum also has an example in their collection which shows Celtic influences:
Finally, one further example, the location of which is unknown to me at the time of writing. This particular example incorporates classic Celtic knotwork with the ancient triskele symbol -- a symbol of eternity.
It seems to me that there is still a great deal that remains to be explored where this tradition is concerned, not least of which in the realm of vestment design.
