Awesome Loki! If you need/want any help let me know...
On another forum I'm on they have a thread for pictures that can be submitted all year(2 pictures per person, each numbered in order to vote on), then around this time of the year they vote for a month, then they have the calendars made in november. When people post their picture to vote on they specify which months they'd like if they win and the person putting it all together makes final decision(to keep it reasonably simple). They then have a page(could be the cover) for an additional say 5-15 vehicles to share that didn't make a specific month. Gives more people the opportunity to "make the cut".
I think the way they do it is spot on.....just some ideas...