Sofie, having a single object on a bookcover can make a striking appearance. Have a look at the different versions of the SCUM Manifesto by Valerie Solanas. In one of the last editions they use a single image in an iconographic way.
https://books.google.co.uk/books/about/SCUM_Manifesto.html?id=KG6lvFPmY0YC&printsec=frontcover&source=kp_read_button&redir_esc=y#v=onepage&q&f=false
