How about some sashing with red cornerstones, then a thin red border and red binding?

Some small pops of lime green here and there would be awesome!

I would like it with sashing in lime green, yellow, red, turquoise ... any color to make the wonderful grey and black blocks pop.

I like as it is, but if you want to add some touch of colour I also vote for aqua or turquoise and maybe a little more white.

I'm all for lime green, as it's fresh and modern. I personally think red with black and white has been overplayed like a good song on the radio.

I would go with white or lime green to make the blocks pop.

there is so much you could do with that! it's cute the way it is, but another color would sure make it pop --- depends on the look you are going for...

What about a red, lime green, or other bright color for sashing between the blocks and border????

I thoroughly agree. If you must have another colour, choose one you will like. Personally I like it as is.
Will you keep building on this to make it bigger? Hope so as a bed size will look awesome.

I also like the monochromatic scheme. Personally, I would not add any other color. And I really like the different sizes of blocks.