I grossly misunderstood the stipulation about minimum aspect ratio and—yes, this doesn’t seem possible—never connected those aspect ratios with the idea of landscape rather than portrait orientation.

So I submitted a few images that were wholly unsuitable (and that were rightly modded out immediately). Subsequently, in poking around, I found the appropriate page in the wiki, giving full detail on upload stipulations.

I didn’t know to whom to apologize for wasting their time, so I’m doing it here: forgive my cloddishness!