I saw this idea on the site http://cursorlibre.com/ where they made a nice dodecahedron with a Ubuntu theme.
In the download package, there is a pdf version ready to print and assemble, plus a pdf version of a guide in which is explained what parts should be cut and how to bend the paper to obtain the dodecahedron.
The calendar has been uploaded at spreadubuntu where you can also download the svg sources and expand the size if you want.
At the moment the calendar is available only in Spanish, i hope that someone good enough with graphic can help in translating it also in other languages.
And if you like it, do not forget to leave a comment on the site of the creator.
Or maybe you prefer a traditional calendar already prepared that you only need to print?
In the latter case, try to look at http://wallpapersku.blogspot.com where you can find a ready to print 12 pictures with Linux theme.
And since I probably forgot to say it to this day … Happy New Year!