The new paper from Graphic 45 "A Place in Time" would be great to use with this format. Graphic 45 also makes chipboard album/easels that would make great calendars. Available in 12x12 and 8x8. Hmmm ... convenient ... they make paper in both those sizes ! ;)
Also ... just in ! packages of American Crafts Cardstock ... 12x12 , 80lb, nice texture one side and smooth on the other, 60 sheets per package for $19.99. That's less than 34 cents per sheet !!
Available in : white, cream, Christmas mix, Pastel mix, black