You could even take the "public domain image" idea and still make something that looks nothing like an O'Reilly book. For example, here are some images from Li

You could even take the "public domain image" idea and still make something that looks nothing like an O'Reilly book. For example, here are some images from Library of Congress with crabs in them that I think could make for interesting book covers: - https://www.loc.gov/pictures/resource/fsa.8a23704/ https://www.loc.gov/pictures/resource/fsa.8a23704/ "Residents of Raceland, Louisiana, eating crabs at crab boil" (1938 Sept.) - https://www.loc.gov/pictures/resource/jpd.00748/ https://www.loc.gov/pictures/resource/jpd.00748/ "Benkeigani to tsubaki" (between 1825 and 1830) - https://www.loc.gov/pictures/resource/ppmsca.69838/ https://www.loc.gov/pictures/resource/ppmsca.69838/ "Frozen crabs at a restaurant" (January 1954) - https://www.loc.gov/pictures/resource/highsm.14204/ https://www.loc.gov/pictures/resource/highsm.14204/ "The Barking Crab restaurant on the Fan Pier across the Northern Bridge from downtown Boston, Massachusetts" (between 1980 and 2006) - https://www.loc.gov/pictures/resource/ds.00242/ https://www.loc.gov/pictures/resource/ds.00242/ "Cancer" (latin name for crab, you'll probably want to edit the image to avoid any unfortunate connotations) (1825) But before picking any of these or other images from the Library of Congress, check the "about this item" link and see in particular the "Rights Advisory", including any links to further details about rights and usage in that field, and keep also in mind things like what is pointed out in one of those links; "Privacy and publicity rights may also apply". IANAL, TINLA.