You see photo galleries all over the web: The top 10 such-and-such photos, or 25 amazing this-or-that pictures. If you’re like us, you click on almost every one of them. Themed photo galleries on blogs work for a simple reason: Almost everyone appreciates great pictures and enjoys sharing them with friends. If you can dream up a good theme, write a good headline, and deliver a payoff of stunning visuals, you’ve got a viral hit on your hands.The difficulty is getting the pictures legally and fairly. You could look for photos on Flickr or Google Images, but you face some time-consuming work: making sure you have permission to republish the pictures. Usually this means contacting every photographer or their agents individually. Some photographers will be delighted that you’re sharing their work, but others will be offended if you fail to give them a say in how the work is presented (or, of course, pay them for it). With rare exceptions (such as NASA images and very old photos), every photograph is copyrighted unless the rights holder says otherwise. You’ve probably read stories about web sites that have had to pull content offline after complaints or legal action from photographers. You don’t want to be in that position.