Does it have to
scream SF?
After all - it will be in the SF section in a book shop.
The meta data will be there for it on Amazon - it will be listed as SF. You are not approaching readers "cold" on this. It is good if it says SF, or doesn't contradict SF... (Doesn't have two girlies in foofy dresses with curly font
)
Now contradicting what I just said a little - trying for the SF look.
In terms of SF - it is in the future with someone with amazing powers. But there are no space ships mentioned in the world building - so having a space ship theme doesn't seem sensible - currently a lot of SF has generic space with or without a space ship pictures even if space ships are a minor part of the plot.
Could be very difficult to have a picture that represents both your story and screams SF.
I think SF ish fonts will help. Could even try just writing SF Thriller on the cover where it currently says "A Jack Stone Book" - though that is not usually done.
However, repeating what I said earlier in the thread - before you finalise what changes you are making - do go and find similar sorts of books to yours and see what the covers are - for editions in the last year or so. You do in part want to represent your book, but you even more want to say to readers "this is another one of those". Now it may turn out that that would be a matter of making it scream SF. Or maybe not. You will also find that when you look at books that have been out for a few years, the covers will have changed - they'll have been re-badged to meet current trends. If you have beta readers, you could ask them for what books you think it is like. It can be hard to pin that down for yourself.
Incidentally, half of the Netforce books are just a computer chip in the background and massive title and author name - no real picture.
So don't just listen to us lot and what we think a cover should be - go look at what is currently selling online.