1. Free sites online:
There are a number of free gallery sites online where you can find many different tattoos, including dragons. Many of the free dragons you'll find tend to be generic designs that you have probably seen before. Nothing too elaborate, elegant, or bold. But if you are looking for a basic design, then a free site might be for you.
2. Tattoo Artists Gallery.
Another option for a dragon tattoo gallery, are individual tattoo artists which have their own site, and specialize in dragons. These can be very unique and original, but there may be a fairly high fee for obtaining each design. Nevertheless you may find a great design that could definitely be worth it.
3. Tattoo Membership Galleries Online.
The best option for a dragon tattoo gallery is usually one which features many different designs listed in various categories. Membership sites provide this. Each category will contain "the best of the best". The category for dragons will contain high quality designs, which work excellent for tattoos. After you find your ideal dragon design, you can always go back and download more designs for future tattoo work. Good galleries will usually have a one time sign up fee, but you will get access to an unlimited number of designs which you can download for present or future ink work.