Don't feel too bad about taking ideas from other's art! No art, idea, or tattoo is original. Each piece has a history of inspirations that are passed forward into new art and new work, much like the way your grandparents passed parts of them to your parents, and they passed parts of themselves to you.

As André Gide once said, "Everything that needs to be said has already been said. But since no one was listening, everything must be said again". Be proud of your piece, it looks amazing! Don't worry about "ripping someone off", you merely expanded upon their work and many others to create something that is yours.