I think a compass is a good way to represent travel. Also, if you get a tattoo in the many places you travel to, what a great souvenir! The Japanese belive that koi fish represent "travelling through life" and they make gorgeous tattoos as well. I always thought that a silhouette of a hiker would be a cool "traveller" tattoo if that's the type of travelling you like to do. Just some ideas I thought of...more to come
A globe or map might be another option, I went with a compass rose but it also had other features which represent a lot more than travel.