I love your idea and I've been wanting to do a full quilt so if I have time I will join you all.
May I make a suggestion for those of you trying to figure out the value of your fabric? It is very hard to know for sure the color values from your pictures because every computer shows colors differently. But if you take a small piece of each fabric (say a 2" square) and lay them on a scanner (all together) then print a gray scale copy of them, you should be able to see the difference in the values and place them from lightest to darkest. This was taught to me by a person who makes quilt portraits.