How can investing energy in the creation of ANY part of the book, ever be considered a waste? I like to have full control; as an artist, writing the text isn't enough. I want a say in the cover. The thing people see first. It's MY work.
Too many books are published with irrelevant stock photo covers - Bred Easton Ellis' "Less than zero" back then, sported a Bullterrier, and I bought it expecting a story about dogs. Waste of money. Yeah, yeah, dog's a metaphor, blah blah, I'm sorry but first impressions should be honest and free from "yay interpretation I'm so edgy".
Or that ever-same bare midsection in sexy/explicit romance. Sometimes it's gay, sometimes it's hetero, but there's always the perfect modelesque bare midsection. This could happen to my WIP despite the dystopian backdrop. Shudder-dee-dudder!
Childhood trauma books? Some random stock kid with a reasonably sad face, photoshopped to look different from the other book it graces.
Now, OP here, has a piece of art that is absolutely capable of competing with Harry Potter and whatever other big book has stunning cover ART (as opposed to "5 minutes on Shutterstuck, another 10 in Photoshop").
I'm no fan of how the dude in the back turned out, but all in all, I don't think anything was wasted here. If any publisher, agent, whatever, decides to go for something else - then they are wasting this gem.
And anyway, I don't get publishers'/agents' hatred for author-submitted cover designs. If it's decent? Why the arrogance of "We have our own designers, hence the author, who only knows how to write what with being the author, can't possibly know better than us what fits the author's story"?
They should at least have a serious, open, honest look before saying "Nope, our designers know better, in all cases without exception".
I'm a hell good artist. I get to have a say in what is put on the front of MY work. If not, I better like the proposal by the designer.
And even if the cover doesn't get picked - any part of creation that adds to the character of the story, including illustrations, is a contribution, not a waste. Ever.
No offense, but if I were an acquisitions editor your attitude would send up so many red flags I'd scurry away. The best artist in the world, btw, doesn't make a good book cover designer. Books are designed to appeal to the marketplace, not the author. I'm a great artist. I wouldn't even pretend to know anything about the cover of a book. FWIW, Tread lightly with megalomania when it comes to dealing with editors. They tend to separate the wheat from the chaff prior to signing.