i told you before that i had ocd when it came to this sort of thing and literally every writer i have come across has the same cover style for all their books because it looks visually pleasing and organized, not boring.
just a few examples: rxmione, regulusblack, potterblacks and pansyparks. on my covers it clearly shows the title and what the fanfic is based off of. you should do the same thing, not have all the same style, but change the covers to something that's easy on the eyes/easy to read. in my opinion.