Well, in terms of the capsule images (the tiny things in the steam listings), the logo is the main thing there. And usually it's pretty much cropped to fit. Steam's guidelines specifically advise against changing the logos and so on, because it harms recognizeability. Just look at how bad the Bioshock Infinite logo looks in the Steam listings, but at least it's recognizeable.
The LARGER steam banners and headers and so forth are what require all that extra design, as you were saying.
Anyhow, I've passed on a bunch of feedback to all the top designs in here, and we'll see what comes of that. Nothing is quite perfect yet, although the successors to #230 have improved immensely and I really like how that turned out.