Try Wikimedia Commons - these photographs are free to use, but you do have to name the source in your hubs with some of the photos. There is a huge collection at this site and the majority of my photos for my hubs come from there. They have selections on everything from buildings to people, so I'm sure you will find a few that are suitable for you. If you can't find what you're looking for in your first search on Wikimedia then change your search words around, it's amazing what different photos will come up. Hope this helps.