Your blocks are nice, but not stunning. What if you actually created a pattern with the blocks? Like put the dark ones in the center in either a pinwheel pattern or with all the HST's in the center? Then try all the same colors around that, maybe with something different in the corners that would lead out to something else? What about using a different sashing in the center both horizontal and vertical to create an interest point? Use that same darker color to emphasize all the lights.
Another idea, use your colors on the diagonal to create color lines in your quilt. Right now, to me, they just look jumbled. One last idea and I'll hush. If your sewing machine has a fancy stitch function, why not quilt your sashing's in an accent color? I would do the dark blue to add pizazz to the project. Put two lines equal distance from each side in the sashing so that you really see them. This can be done after you have completely finished the quilt.