I have successfully done this a few times. My approach, which has worked every time, is this:
Don't delete the older image already up on SS. Leave it there for now.
Submit the new one with a note to the reviewer explaining that the image is already available on SS as #12345678, but that you've improved it in such-and-such a way. Tell the reviewer that if the new version is approved, you will delete the older version.
Wait until the new one is approved (assuming it is), then delete the original as promised.
Good luck!