The white sets the blocks better. But, if you want to add more color and warmth, why not consider cornerstones of reds? I see several reds, oranges and yellows in the shirts. Adding the 9 or 12 little spots of color would warm it up without distracting. I would then do a framing border of white. At that point you can decide whether you want to stop there or perhaps add another borders of one of the colors.