How would you distinguish an older preview from a pending car concept?

I am thinking through an interface-state question, not reporting a measured production bug. When an image-editing application has a history view and a new result is pending, should its last completed preview stay visible with an explicit label, or be replaced by a loading state?

For context, I am associated with Car Customizer, a browser-based AI vehicle-appearance tool with comparison, history, continued editing and downloads. It accepts JPG, PNG and WebP photos up to 10 MB, with paint, wheels, wraps, stance, body-kit and spoiler directions:
https://car-customizer.online/

Here is a proposed synthetic fixture: candidate A is visible; request B is pending; then the user deliberately selects older candidate C from history before B completes. I would expect B to become an available history entry, rather than silently replacing C. This is a design example, not a claim that the current website behaves incorrectly or has already implemented a particular job model.

Would you keep generation-job identity separate from selected-candidate identity? A label such as "New result ready in history" could describe completion without implying that the currently displayed image changed. The download action and its filename should refer to the candidate actually selected, not simply to the most recently completed request. I am interested in how this would remain understandable for keyboard navigation and screen-reader announcements as well as visual users.

I would test the transitions with local stub images and a deterministic completion order, rather than repeatedly generating paid results. New accounts receive nine welcome credits once, not a recurring free allowance; later generation may require paid credits or a subscription. A timing or selection mistake should not be resolved by quietly spending more credits.

Would you prefer an explicit "older preview" panel while processing, a separate pending card, or a blank preview until completion? What state invariant would you test first? This question was prepared with AI assistance and project affiliation is disclosed above. Visual vehicle concepts do not establish physical fitment, installation safety, exact paint color or road legality.