I think you really should go to a shop. You do realize that part of what you are paying for is to have a real live artist draw up whatever your brain can think of. On top of that they will have to "redraw" the tattoo at least once (think they are "drawing" the tattoo on you", otherwise to tracing paper then to your skin).
Getting ideas from online is not a bad idea. You can hone in on an idea that you like (for example, looking up a bunch of dragons). You can print out some references to bring to your artist so you can visualize what what you were thinking.
Remember images sometimes look killer on paper but you are not a piece of paper. You are an organic, moving, not even close to flat, pre-colored (skin tone) object. Your artist will take all of this into account with your provided reference material to give you a killer tattoo.