Thanks for the comments, WereSpielCheckquers and Platonides!
1. I am not sure whether we'll be including file descriptions at all this year; it was the only thing besides the last page that made the calendars not language-neutral. This is something we try to avoid as much as possible, as we're having WLM in more countries that use non-Latin alphabets than last year.
I'm not saying "no" to descriptions in English, but this /is/ a problem, and we will not be able to translate them into the 37 languages used in WLM countries, especially due to technical and financial reasons. If you'd prefer to have the descriptions below the photos, I'll make sure to have them in a bigger font than last year :-))
2. The names of the authors are listed on the last page of the calendars, though as Platonides rightly pointed out, we forgot to include a link to the page of the deed at creativecommons.org; this is something we can improve this time.
I am not sure whether adding a link to a winning photo would be useful at all, especially with long filenames or filenames written in non-Latin alphabets (or even in Latin alphabets in countries which use different ones); just imagine how long would typing those from your keyboard take!
And by the way, the forward slashes // were just part of the design, with no special meaning.
3. You cannot buy a copy of the 2012 calendars (I'm quite sure there are no spare copies left at all), and I haven't heard about any plans of selling the 2013s to the public. You'd be able to buy (or get) those from a local chapter if they order more than they really need.
Last year, a Wikimedia Polska representative gave more than 10 copies to the Wikimedia Foundation staff at the financial meeting in Paris; I've heard they liked them :-) so if the Foundation would like to sell the 2013s in their shop, they will be able to download the design file from Commons -- we'll upload it there as soon as we have it ready, just like I did with the one we used this year.