Whooping Crane (2011) by Smithsonian Institution. Original from Smithsonian's National Zoo. Digitally enhanced by rawpixel. https://www.rawpixel.com/image/3060032/free-photo-image-crane-amazing-animalFree Image from public domain licenseA Racer - long and slim. [Lake Winnipesaukee, New Hampshire] by Willis G C Kimball https://www.rawpixel.com/image/14295224/photo-image-face-person-waterFree Image from public domain licenseWilliam Purdie Dickson, D.D., Professor of Biblical Criticism by Thomas Annan https://www.rawpixel.com/image/14319683/william-purdie-dickson-dd-professor-biblical-criticism-thomas-annanFree Image from public domain licenseA group of children are playing on a gate in a woodland. Engraving by C. Cousen after W. Collins. https://www.rawpixel.com/image/13984200/image-face-plant-personFree Image from public domain licenseFree Hong Kong city skyline at night image, public domain travel CC0 photo. https://www.rawpixel.com/image/5901776/photo-image-public-domain-free-cityFree Image from public domain licenseFree two baby sheep standing on grass field image, public domain animal CC0 photo. https://www.rawpixel.com/image/5912261/image-background-public-domain-greenFree Image from public domain license"Mignard", Statue by Jean Baptiste Joseph de Bay, Decoration of the Louvre, Paris by Édouard Baldus https://www.rawpixel.com/image/14324174/image-face-person-bookFree Image from public domain licenseGeorges Simon Serullas. Halftone after lithograph by Palley. https://www.rawpixel.com/image/14004948/georges-simon-serullas-halftone-after-lithograph-palleyFree Image from public domain licenseUnidentified Union soldier with moustache, printed in vignette-style by Frederick Gutekunst https://www.rawpixel.com/image/14307928/image-face-person-artFree Image from public domain licenseFree close up design text on computer screen image, public domain CC0 photo. https://www.rawpixel.com/image/5921036/photo-image-background-public-domain-freeFree Image from public domain licenseUnidentified man with graying beard, no moustache, in profile, printed in vignette-style by Mathew B Brady https://www.rawpixel.com/image/14307797/image-face-person-artFree Image from public domain licenseFree black and white heating plant photo, public domain grayscale CC0 image. https://www.rawpixel.com/image/5922848/photo-image-public-domain-free-black-and-whiteFree Image from public domain licenseGolden Poison Frog (2016) by Chris Wellner. Original from Smithsonian's National Zoo. Digitally enhanced by rawpixel. https://www.rawpixel.com/image/3060570/free-photo-image-frog-yellow-amphibianFree Image from public domain licenseMurillo. L'enfant Jesus et St. Jean. Les enfants a la coquille (au Musee du Prado) by Juan Laurent https://www.rawpixel.com/image/14278444/image-face-jesus-personFree Image from public domain licenseHorace Wells. Photograph of reproduction of stipple engraving by H. B. Hall. https://www.rawpixel.com/image/13987987/horace-wells-photograph-reproduction-stipple-engraving-hallFree Image from public domain licenseAn Indian papoose in a baby carrier. Colour process print, ca. 1903. https://www.rawpixel.com/image/13963998/indian-papoose-baby-carrier-colour-process-print-ca-1903Free Image from public domain licenseJohn Burns. Photograph after a painting by J. Graham-Gilbert.. https://www.rawpixel.com/image/14009993/john-burns-photograph-after-painting-graham-gilbertFree Image from public domain licenseFree close up baby goat's head image, public domain animal CC0 photo. https://www.rawpixel.com/image/5911149/photo-image-background-public-domain-greenFree Image from public domain licenseFree brown bear mother with her cub on the hill public domain CC0 photo. https://www.rawpixel.com/image/5908282/image-background-public-domain-natureFree Image from public domain licenseUnidentified older man with a long beard, a pince-nez around his neck by Peter S Weaver https://www.rawpixel.com/image/14306867/image-face-person-artFree Image from public domain license