Thanks Erick - it's something I've never tried (drawing on card board) - so I'm learning something new here! Now that I think about it - it does seem a good choice because it's a pretty robust material.
i had about 4) 24" x 16 pieces of card board left over from the 2011 calendars so i decided it give it a go. been pretty happy with how everything is coming out. it's actually pretty fun too, some the stuff kind of has that graffiti feel to it which for an old school head like me is cool.