I'd be interested in buying one if it was under $20.
Also, I have seen several calendars that are 15 month. So as a collector 1st addition you could make a 15 month that includes Oct 2012 - Dec 2013. If it goes over well enough, just make 12 month calendars after that.
My vote for content would be: let people post up pictures they think would go into the calendar, then let everyone else vote. The top 12 (or 15) get in the calendar. Set a deadline date for submissions and voting. On the final date the most votes on submissions win. Warning: This is going to be a monster sized thread! Maybe have a special group (Ryan, or moderator group) have final say in order to keep a common theme or format.
I also think all the pictures should be garage related. If a member wants to showcase their car, project, or wife, it should be pictured in their garage or in front of their garage. I have already seen many awesome pictures on here like this. The votes would decide if it's good enough for the calendar.