There are a lot of other things that are symbolic of Gemini, from flowers to Countries.
All of the following relate to Gemini:
Birds: Parrots, parakeets, minah birds
Flowers: Lavender, Lily-of-the valley, myrtle, fern
Nuts: Horse chestnuts
Countries: Wales, Belgium, USA, Egypt
Cities: London, San Francisco, Melbourne
Ruling Planet: Mercury
As you are an air sign & very versatile and adaptable, I should think that you'll be after quite a unique tattoo design that says something about you.
If you try and get ideas from the free online gallery sites, then you're not going to get a lot of choice or anything very inspiring. Best to get the biggest choice of Gemini tattoo designs possible by going to an award winning online gallery that offers thousands of designs that are constantly being updated.
You could even be 'different' and have a monkey tattoo for example and when people ask you why, you can explain that it's because you're a Geminian, certainly a conversation starter. If you don't fancy anything quite so bold, why not just have the Gemini glyph as a tattoo. This is two upright parallel lines with a line across the top & bottom. You could have that on its own or with something entwined around it.
The area of the body associated with Gemini is the shoulders & arms, both ideal places for Gemini tattoo designs as shoulder & arm band tattoos are very 'in' at the moment.
Source : http://ezinearticles.com/?Gemini-Tattoo-Designs---List-of-Ideas&id=1101543