My understanding is that yes, you can keep the same cover. I think they give you a budget for the cover art, and you’re free to hire whoever you like; I think that’s what happened with
@JF Dubeau’s "The Life Engineered" ... I don’t know how much leeway you get with that, though. They might have an option where you let them hire an artist, but you still get a say in how the cover design goes. I know
@Richard Heinz was talking in an update about choices in direction for his cover art. He would know more.
If you hire an artist, you’d have to pay them for their work upfront. Sure, it may suck if the work weren’t actually used in the end, but I think most artists would be pretty okay with that as long as they’d been properly paid for their work: you’ve bought it, it’s yours now, and you can do what you like with it.
For myself, a friend volunteered to do my cover for me--I learned later that he does this sort of thing professionally. I’ve offered to pay him, but he said he wouldn’t ask money for something he volunteered to do. The plan is to keep his cover for the final project, but I might demand small changes just so I have an excuse to pay him then.
