The idea of a calendar has been discussed at least twice in the past. I think the general consensus that it would incur significant costs to set up and would only achieve sufficient sales to make it worthwhile if a decent proportion of the participants were women. I got as far as designing some of the months (with groups of participants involved in relevant activities) and working out potential locations but if all the nudity is male I doubt we’d sell more than around 10-20 copies. With female involvement, that could increase many fold.
A few people suggested individual photos sent in by members of this community, but I cannot imagine that being marketable or reliably high enough photographic quality.