Central to Celtic culture is the Celtic knot. Knot designs, most representing an endless loop, were used primarily for decoration. Although the variety and design of knots is as endless as the imagination, there are a few very basic designs upon which all others are based. When considering a Celtic knot tattoo, you can either pick one that has a design you find attractive, or you can be bold and design one yourself.
Almost as ubiquitous as the Celtic knots are the Celtic hounds. Hounds were prized by royalty and warriors and held a place of honor in many legends. A multitude of Celtic hound designs can be found in ancient manuscripts and are reproduced in many art books. As with Celtic knots, if you are considering a hound tattoo there are plenty of predesigned images to choose from, or you could try your hand at designing your own.
Contrary to popular belief, the Celts never used runes. However, there was an ancient Irish system of writing that closely resembles runes, called Ogham. Any word or phrase can be written in Ogham and turned into a tattoo.