Yeah, that F5 trick is a bother, sometimes, and I've found that there are occasions where no matter how many times I hit F5 or empty my cache, the bad image remains. I give it another hour (or switch computers), and all is well again.
Unfortunately, our current approval queue system isn't great for giving feedback on approvals/rejections. There are many times where the options don't fit what I want to say. For instance, some images may be of higher quality, but the angle at which the item is show (we prefer straight on, as if it were scanned) is most often preferred, even if the original is of slightly less quality. We don't have a an option that quite fits that explanation.
Other image rejections might be due to the content of the photo itself. I rejected some of your Twilight Princess LE images because we prefer the front of the regular box to be the main image. An image with the game and the amiibo itself are acceptable in the cart/media image category as we allow this for items that are a "bundle" of items.
It's a number of us who work with approvals, so I think it's fine to make a forum post if you're curious why something wasn't approved. Mistakes by the admin certainly do happen, though we try our best to research our decisions to approve or reject.