If that’s the type of single packaging I’m thinking of (which I’ve seen on a couple singles I’ve imported from Japan), there isn’t a back cover image there. One side of the single has the CD showing; the other side has the title pane of that card showing. The half-width spine is visible; the rest is folded and hidden inside the case, not visible without opening it.
Sometimes that card also has a back side, if it does I’d suggest scanning & uploading it too.
I think it’s OK to upload an additional “front” image from cutting only that pane. Or of course if OP doesn’t want to (and I see no reason to expect it), anyone else can download the image, cut it, and upload it.