The publisher is in charge of the cover. Sometimes, depending on the publisher, they’ll ask for input (what covers the author likes or what they would like for their book), or they’ll show the author a cover comp (an example direction) and ask for feedback. Sometimes if an author hates the cover they can give input and perhaps the publisher will go in a different direction, but usually the cover decision lies with the publisher’s art department.
Hullo and thank you for answering all these questions! I hope this isn't a dumb question, I've always just kind of wondered about this. So who picks the cover when books are ready to go out into the "world?" Hypothetically, would I be able to choose what my cover looks like for my book? Cheers!— Anonymous