All my pictures are licensed under the Creative Commons Non-Commercial Non Derivative license. This license is often called the “free advertising” license because it allows you to download my work and share it with others as long as you mention me and link back to me, but you can’t change my work in any way or use it commercially.
Creative Commons is a non-profit organization devoted to expanding the range of creative work available for others to build upon and share. Current copyright laws are generally extremely restrictive. Creative Commons has done the hard legal figuring to enable people to simply and easily express their preferences with respect to what others can do with their work.