Guild Challenge - need help.

My Guild is going to do a Quilt Show in 2015 and as part of the preparation, they set up a challenge called "Back to Basics".   The challenge is to make a 24" by 24" quilt that uses a well known quilt block.  You use only two colours or variations of those colours that you picked out of a bag.  I got purple and green.  When done you include the name of your quilt block on your label.  That's it.

I was considering just doing squares and making another pixelated quilt like this diagram that I made

 Using these colors

(it's Violets because of the purple and green), but it's not a traditional quilt block but it does do just squares.  The question is can I do this?

Or I can do this one. the Midnight Garden by McCalls.

Could do it in purple.  

See my material?  What do you think.  I need help!!!