VOL1 is likely referencing the Pulp Fiction (1994) Cover
Edit: it is lmao
source
the other covers are also referencing movies
VOL2 - Léon: The Professional
VOL3 - Breakfast at Tiffany's
VOL4 - Buffalo '66
VOL5 - Amélie
VOL6 - Enter the Dragon 1973
as for VOL7, the author didn't state...