Interesting! Welcome to the forum, by the way. Is your sister also getting a tattoo? If so, are you getting matching tattoos? One idea is using her zodiac for your tattoo. There are some very nice celtic symbols that you could use. Have you searched any celtic symbols out? I love them and there are some that could be used to represent your relationship with your sister. What are some of her passions and interests? That is one way to honor her as well. Anyway, I don’t have anything real concrete off the top of my head. I’m sure you will get lots of responses to this post. Good luck! :):)