well, the simple answer is that there is no way to put up your pic on here, without someone simply being able to save it!!
So, you've got two main choices.....
1) Make the pic really small so that you can make out what it is, but so that if they saved it and then tried to make it bigger, then it would just go all blurred
2) Put a watermark in it, so that its not really usable by anyone, but they can get an idea of the photo. A lot of professional photographers use this method, such as wedding photographers etc. They'll put their pics online, basically so you can pick the ones you want, then order them, but as they stand online with a watermark through them, you're not likely to print it and put it in a frame!!