If you scroll down to the bottom of your personal.ini you can do this:
Code:
[https://archiveofourown.org/works/######]
never_make_cover:true
I do this for a few stories with high-res covers I don't want overwritten, and a few others with NSFW artwork that keeps getting used as covers.
I think there may also be a way to set it to a custom URL/filepath but I am not entirely sure.