Hey, awesome to see how this is coming along.
I'm torn about putting all of the infoboxes off to the right. On the on hand, it seems useful as a way of getting information to people efficiently. On the other hand, having a thin link bar on the left and a much thicker infobox bar on the right throws the balance of the page off, and makes all of the text and images feel kind of squished in the center. As was said below, a way to collapse that bar (and have the text spread back out into that space) would be nice. I think it should default to having the bar open each time you go to a page, though (i.e. if I go to autumn, collapse the bar, go to summer, and then go back to autumn, the bar should be expanded again).
I went to the page en:And Yet It Moves, and noticed that the Reception template (the one that details the review scores) has been moved to the right. The word "Reception", however, is still where the template was originally, and is surrounded by a whitespace gap. This might be because that word is part of the trigger to collapse the table down.
On the plus side, I actually went to that page to check on how Winter handled en:Template:multiple image, and it looks awesome. It was rapidly becoming one of my favorite toys before, and Winter will only make me want to use it more.
Lastly, I wanted to suggest that you use a circle with a plus in it, instead of a star, for indicating Good Articles in the box up at the top of the right bar (And Yet It Moves has one). Stars are the domain of Featured content (articles, pictures, portals, and topics), and I'd rather not use them for Good Articles because there can be a pretty sizable quality gap between GAs and FAs.