Look at other calendars. Put some of your very best pictures together and send them to a calendar publisher. In the worst case they do not publish them. In the best case you get some money
Do you know the "Literarischer Katzenkalender". I know that the publisher Ida Schöffling always wants new and unusual cat pictures. I think some of Lily jumping from cupboard to cupboard would be purrfect. Now is a good time for the 2011 calendar