If you like the dark blocks, if you have the fabric, as opposed to using a charm pack:
think about this, add one more black and one more of the same color as the upper right. Use these 4 (2 black, 2 black prints) as cornerstones in opposite corners to each other.
Add 3 more of the dark print 2nd from right on the bottom. Use these four as next in, diagonally from the other 4 cornerstones.
This adds 5 blocks, so your layout will be 7x5 instead of 6x5.
As for sashing, I like dunster's suggestion of light with yellow cornerstones.
If you have trouble visualizing different sashes, lay the sash fabric on a bed, or your design wall, and arrange the blocks on top of the sash fabric. Auditioning the fabric, you can literally see the effect.
Oh, and last, but not least, your blocks are quite pretty, and your work putting them together is excellent! Lovely colors.
Last edited by quiltmouse; 07-22-2014 at 09:35 AM.