A silhouette image is just a solid shape representation of an object. It is usually black. A silhouette image or photography can be produced by capturing an object against a bright light casting on the object. That is viewing the object from the direction just opposite to the direction of the light casting on the object. Find here some best silhouette images, pictures that can be shared online and used for non-commercial uses.
The term silhouette was seldom used until the early decades of the 19th century. However, the term silhouette became popular in the 20th century and continued in the 21st century. You could see here some best and top rated silhouette images portraying different images of life, nature, animals, people, etc. Just scroll down and select the best ones to use in your applications for non-commercial purposes.